Geothermal Power: Common Questions Answered, Including Electromagnetic Interference Concerns

Home Geothermal System 1. Photo by James Finn ©2023

The first practical geothermal question most people ask me is, “How deep and wide does the hole need to be dug for a home geothermal system?”

Here’s my answer: The depth and width of the hole that needs to be dug for a home geothermal system will depend on several factors, including:

1. Type of system: There are two main types of geothermal systems for homes: ground-source heat pump systems and direct-use geothermal systems. The depth and width of the hole will depend on the type of system you choose.

2. Climate: The depth and width of the hole will also depend on your local climate and the average temperature of the ground at your location. In colder climates, the hole may need to be deeper to access warmer ground.

3. Soil conditions: The soil conditions at your location will also play a role in determining the depth and width of the hole. For example, if you have rocky or sandy soil, the hole may need to be wider to accommodate the installation of the pipes.

4. System size: The size of the geothermal system you choose will also impact the depth and width of the hole. Larger systems will typically require deeper and wider holes to accommodate the increased number of pipes and other components.

Home Geothermal System 2. Photo by James Finn ©2023

As a general rule, a home geothermal system typically requires a hole that is between 100 and 400 feet deep and between 4 and 6 inches in diameter. However, these are rough estimates, and the exact depth and width of the hole will depend on the specific conditions at your location and the type of geothermal system you choose.

It is recommended that you work with a licensed and experienced geothermal contractor who can assess your specific needs and provide an accurate estimate of the depth and width of the hole required for your home geothermal system.

Geothermal power systems for homes typically use the constant temperature of the earth as a source of energy to heat and cool a building. There are two main types of geothermal power systems for homes: ground-source heat pump systems and direct-use geothermal systems.

1. Ground-Source Heat Pump Systems: These systems use a heat pump to transfer heat between the home and the ground. The system consists of a ground loop (a series of pipes buried in the ground), a heat pump unit inside the home, and a distribution system (e.g., ducts or radiant flooring) to distribute the heat.

Components:

• Ground loop

• Heat pump unit

• Distribution system

Pros:

• Energy efficient: Ground-source heat pump systems are typically more efficient than traditional heating and cooling systems.

• Renewable energy: Geothermal energy is a renewable resource, so these systems reduce reliance on non-renewable energy sources.

• Long lifespan: Ground-source heat pump systems have a long lifespan and require little maintenance.

Cons:

• High upfront cost: The initial cost of installing a ground-source heat pump system can be high.

• Limited availability: Geothermal resources are not available everywhere, so these systems may not be suitable for all locations.

Costs:

• Purchase cost: Ground-source heat pump systems typically cost between $7,500 and $25,000, depending on the size and complexity of the system.

• Installation cost: Installation costs can range from $10,000 to $25,000, depending on the complexity of the installation and local labor costs.

  2. Direct Use Geothermal Systems: These systems use hot water from geothermal wells or springs to directly heat a building. The hot water is typically piped directly into the building and used for heating, hot water, and/or industrial processes.

Components:

• Geothermal well or spring

• Piping system

• Heat exchanger

Pros:

• Direct use of hot water: Direct use geothermal systems use hot water directly, which can be more energy efficient than using a heat pump.

• Suitable for certain locations: Direct-use geothermal systems are best suited to locations with hot water resources.

Cons:

• Limited availability: Geothermal resources are not available everywhere, so these systems may not be suitable for all locations.

• High upfront cost: The initial cost of installing a direct-use geothermal system can be high.

Costs:

• Purchase cost: Direct-use geothermal systems typically cost between $10,000 and $50,000, depending on the size and complexity of the system.

• Installation cost: Installation costs can range from $15,000 to $50,000, depending on the complexity of the installation and local labor costs.

These are the main types of geothermal power systems for homes, along with some of their components, pros, cons, and costs. It's important to note that the actual costs and feasibility of these systems can vary greatly depending on local factors such as climate, geology, and regulations.

Home Geothermal System 3. Photo by James Finn ©2023

Here is more detail on the components of a ground-source heat pump system:

1. Ground Loop: The ground loop is a series of pipes that are buried in the ground near the home. The pipes are filled with a water-based solution (or refrigerant in some cases) that transfers heat to or from the ground, depending on the desired heating or cooling effect. There are two main types of ground loops: horizontal loops and vertical loops. Horizontal loops are typically used for residential systems and are installed by digging trenches in the ground. Vertical loops are typically used for commercial systems and are installed by drilling wells into the ground.

2. Heat Pump Unit: The heat pump unit is located inside the home and is responsible for transferring heat between the ground loop and the home. The unit consists of a compressor, a heat exchanger, and an expansion valve. The heat pump unit works by compressing the refrigerant in the heat exchanger to increase its temperature and then transferring the heat to the home through the distribution system.

3. Distribution System: The distribution system is responsible for distributing the heat (or cooled air) throughout the home. This can be done through ducts and air handlers (for forced air systems) or through radiant flooring or radiators (for hydronic systems). The distribution system is designed to maximize the efficiency of the heat pump unit and ensure that the heat is evenly distributed throughout the home.

These are the main components of a ground-source heat pump system, and they work together to provide efficient heating and cooling for a home. It's important to note that there are many different designs and configurations of heat pump systems, and the specific components and design of a system will depend on factors such as the size of the home, local climate, and the preferences of the homeowner.

Home Geothermal System 4. Photo by James Finn ©2023

Ground-source heat pump systems utilize the consistent temperature of the ground to heat and cool a home efficiently. A network of underground pipes circulates a mixture of water and antifreeze, which transfers heat to or from the home as needed. This system is highly energy efficient and can also provide hot water.

Direct-use geothermal systems use the naturally warm water from geothermal wells for heating and sometimes for producing hot water. This water is pumped directly into the home and does not require any heat exchange. This system is ideal for homes located near geothermal wells and is often used for radiant floor heating and hot water heating.

What are the pros and cons of a Direct-use geothermal system?

Pros:

• High Efficiency: Direct-use geothermal systems utilize natural heat from the earth, making them highly efficient and reducing energy consumption and costs.

• Reliable: This type of system is very reliable as it does not rely on any external energy source, such as fuel or electricity.

• Environmentally Friendly: Direct-use geothermal systems do not produce any greenhouse gas emissions, making them a clean and environmentally friendly option.

• Low Maintenance: This type of system requires minimal maintenance, as it does not have any moving parts and operates underground.

Cons:

• Limited Availability: Direct-use geothermal systems are only feasible in certain areas where geothermal wells are accessible, and the water is warm enough for heating purposes.

• High Initial Cost: The cost of drilling a geothermal well can be high, making the initial investment for a direct-use geothermal system relatively high.

• Limited Functionality: Direct-use geothermal systems are only used for heating and hot water, whereas a ground-source heat pump system can also provide cooling.

• Well Drilling Risks: The process of drilling a geothermal well carries some risks, such as the potential release of harmful gases or the contamination of underground water sources.

The cost of a direct-use geothermal system can vary greatly depending on several factors, such as the location, size of the home, and the complexity of the installation.

Equipment costs:

• Geothermal Well: The cost of drilling a geothermal well can range from $10,000 to $30,000 or more, depending on the depth and location.

• Heat Pump: A heat pump is required to circulate the warm water from the well to the home, and its cost can range from $2,500 to $7,500.

• Pipes and Insulation: The cost of pipes and insulation can vary, but it can be around $1,500 to $4,000.

Installation costs:

• Installation of the well, heat pump, and pipes can cost between $20,000 to $50,000 or more, depending on the complexity of the project and the location.

It is important to note that these costs can vary greatly and that it is always best to get a detailed quote from a qualified geothermal contractor. Additionally, the high initial cost of a direct-use geothermal system is often offset by long-term energy savings and low maintenance costs.

Heat Pump:

A heat pump is a central component of a direct-use geothermal system. It circulates the warm water from the geothermal well to the home and is responsible for extracting heat from the water and transferring it to the home for heating purposes. Heat pumps come in different sizes and configurations, but the most common types used in direct-use geothermal systems are air-source and water-source heat pumps.

Air-source heat pumps use the outdoor air as the source of heat, while water-source heat pumps use the water from the geothermal well. Both types of heat pumps work by using a refrigerant to transfer heat from one location to another. In the case of a direct-use geothermal system, the heat pump circulates warm water from the well to the home and transfers heat to the home's heating system.

Pipe Insulation:

Pipe insulation is used in a direct-use geothermal system to prevent heat loss as the water is circulated from the geothermal well to the home. The insulation helps to keep the water at a consistent temperature, which improves the efficiency of the system and reduces energy consumption.

There are different types of insulation materials available, including foam insulation, fiberglass insulation, and closed-cell insulation. The type of insulation used will depend on the specific requirements of the system and the local building codes. It is important to use high-quality insulation that is designed for underground use, as it must be able to withstand the harsh conditions of underground installation.

Several types of foam insulation can be used for underground pipes in a direct-use geothermal system, including polyurethane foam and polyethylene foam.

Polyurethane foam is a closed-cell foam that is known for its high insulation value, durability, and resistance to moisture. It is often used for underground pipe insulation due to its excellent thermal performance and ability to withstand the pressure of the surrounding soil.

Polyethylene foam is another common choice for underground pipe insulation. It is a lightweight, flexible, and closed-cell foam that is easy to install and provides good insulation properties. It is also resistant to moisture and has a low thermal conductivity, which makes it a good choice for geothermal applications.

The type of foam insulation used in a direct-use geothermal system will depend on several factors, such as the local building codes, the climate, and the specific requirements of the system. It is best to consult with a professional geothermal contractor to determine the most appropriate type of insulation for your system.

Closed-cell insulation is a type of insulation material that is made up of small, tightly packed cells that are filled with a gas, such as air, or a proprietary blend of gases. The cells are closed, meaning that the gas is trapped inside and cannot circulate freely, providing excellent insulation properties.

Closed-cell insulation is known for its high insulation value, making it a good choice for applications where high thermal performance is required. It is also resistant to moisture, which makes it a good choice for underground installations, such as in a direct-use geothermal system.

Closed-cell insulation is typically denser and stiffer than open-cell insulation, making it a good choice for applications where structural support is required. Additionally, because the cells are closed, it has a higher resistance to air infiltration and can provide a vapor barrier, making it a good choice for applications where airtightness is important.

Overall, closed-cell insulation is a versatile and effective insulation material that is widely used in a variety of applications, including building and construction, industrial and commercial applications, and geothermal systems.

The type of gas used in closed-cell insulation can vary depending on the manufacturer and the specific product. Some of the most common gases used in closed-cell insulation include:

• Air: Air is the most common gas used in closed-cell insulation and is often used in polyurethane foam insulation.

• Argon: Argon is an inert, colorless, and odorless gas that is often used in closed-cell insulation due to its excellent insulation properties.

• Krypton: Krypton is another inert gas that is often used in closed-cell insulation due to its high thermal resistance.

• Xenon: Xenon is a rare, inert gas that is used in closed-cell insulation due to its high thermal resistance and insulation value.

It is important to note that some manufacturers use proprietary blends of gases to enhance the insulation properties of their products. These blends can be optimized to provide the best combination of insulation value, moisture resistance, and durability.

The specific gas used in closed-cell insulation will depend on the manufacturer, the product, and the specific requirements of the application. Consult with a professional insulation specialist to determine the best type of gas for your needs.

What are the potential hazards of using geothermal energy production?

Yes, there are potential hazards associated with geothermal energy production, although these are generally minor compared to the benefits of this clean, renewable energy source. Some of the most common hazards include:

• Hydrogen Sulfide Gas: Hydrogen sulfide gas is a byproduct of geothermal energy production and can pose a health risk if not properly managed. In high concentrations, hydrogen sulfide gas can be toxic and can cause respiratory problems, headaches, and dizziness. It is important to install proper ventilation systems and monitor hydrogen sulfide levels to ensure the safe operation of a geothermal energy system.

• Earth Tremors: Geothermal energy production can sometimes cause small earth tremors, although these are generally minor and do not pose a significant risk. In some cases, geothermal energy production has been associated with increased seismic activity, although this is relatively rare.

• Environmental Impacts: Geothermal energy production can have impacts on the local environment, including changes to water quality, soil and air quality, and wildlife habitats. It is important to carefully manage and monitor these impacts to ensure that geothermal energy production is sustainable over the long term.

• Corrosion: Geothermal energy production can result in increased levels of corrosion, which can affect the longevity and performance of equipment and infrastructure. It is important to use corrosion-resistant materials and coatings to prevent this type of damage.

Overall, geothermal energy production is considered to be a relatively safe and environmentally friendly form of energy production, and the hazards associated with this technology are manageable with proper planning and management.

Here are a few companies that install geothermal systems for homes in the Dallas, Texas area:

1. EcoGeo Solutions

2. TGE Technologies

3. Skyline Innovations

4. Green Energy Solutions

5. Prime Mechanical

6. Texas Geothermal Solutions

7. H&H Environmental Services

8. Texas Renewable Energy

9. WaterFurnace Southwest

10. Earth Energy Solutions

Here are a few companies that install geothermal systems for homes in the New York Tristate area:

1. Advanced Geothermal Systems

2. Geothermal Experts

3. Tri-State Geothermal

4. Earth Energy Solutions

5. Green Energy Solutions

6. Energy Geothermal

7. Infinity Renewables

8. Climate Control Heating & Air Conditioning

9. Naughton Energy

10. R.A. Snyder Services

Here are a few companies that install geothermal systems for homes in the Los Angeles, California area:

1. Cal-Tech Heating & Air Conditioning

2. California Geothermal

3. Geo-Thermal Solutions

4. Green Energy Solutions

5. Sunset Air

6. SoCal Geothermal

7. Energy Geothermal

8. Infinity Renewables

9. EcoGeo Solutions

10. LA Geothermal Solutions

It is important to note that this list is not exhaustive, and there may be other companies in these areas that offer geothermal installation services. Before choosing a company, it is recommended that you research their experience and reputation and get multiple quotes to compare prices and services. Additionally, it is recommended that you work with a licensed and insured contractor to ensure the quality and safety of your geothermal system installation.

Here are some potential drawbacks of using geothermal energy for a home:

1. Initial Costs: Installing a geothermal energy system can be expensive, with costs ranging from $20,000 to $50,000 or more. This may make it less accessible for some homeowners, especially those on a tight budget.

2. Complexity: Geothermal systems are complex and require specialized knowledge and skills to install and maintain. This can make it difficult for homeowners to perform their own maintenance or repairs and may require them to hire a professional contractor.

3. Location-specific: Geothermal energy systems require access to geothermal resources, such as hot springs, geysers, or volcanic activity. This means that not all homes will be able to use geothermal energy, and the suitability of the technology will depend on the local geography and geology.

4. Limited Capacity: Some geothermal systems may have limited capacity and may not be able to generate enough energy to power a home during periods of high demand.

5. Environmental Concerns: Geothermal energy systems can have some environmental impacts, such as the release of greenhouse gases and changes to water quality in the vicinity of geothermal wells. Additionally, the installation of geothermal systems may result in the disturbance of natural landscapes, including the removal of vegetation and the excavation of land.

It is important to note that these potential drawbacks will vary depending on the specific system, location, and other factors. Before choosing a geothermal energy system, it is important to carefully consider the costs, benefits, and potential drawbacks of the technology and to work with a licensed and experienced contractor to ensure the quality and safety of your installation.

Here are some long-term benefits of using geothermal energy to power a home:

1. Energy Efficiency: Geothermal systems are highly energy efficient, with efficiency ratings that can be as high as 400%. This means that they can generate more energy than they consume, reducing the amount of energy required from other sources.

2. Cost Savings: Geothermal systems can result in significant cost savings over time, as homeowners can reduce their dependence on more expensive forms of energy, such as electricity from the grid or heating oil.

3. Reliability: Geothermal systems are reliable and can provide consistent and continuous heating and cooling with minimal maintenance. This means that homeowners can count on their systems to keep their homes comfortable and energy efficient, even during periods of extreme weather or power outages.

4. Environmentally Friendly: Geothermal systems are considered to be environmentally friendly, as they produce very low emissions of greenhouse gases and do not rely on the burning of fossil fuels.

5. Longevity: Geothermal systems are long-lasting and can last for decades with proper maintenance. This makes them a smart investment for homeowners who want to reduce their energy costs and minimize their environmental impact over the long term.

It is important to note that the specific benefits of using geothermal energy to power a home will depend on the specific system, location, and other factors. Before choosing a geothermal energy system, it is important to carefully consider the costs, benefits, and potential drawbacks of the technology and to work with a licensed and experienced contractor to ensure the quality and safety of your installation.

What are the potential electromagnetic issues with using geothermal power for a home?

There are no significant electromagnetic issues associated with using geothermal power for a home. Geothermal systems work by tapping into the heat stored in the earth to provide heating, cooling, and hot water for a home. Unlike other types of energy generation, such as fossil fuels or nuclear power, geothermal systems do not generate significant levels of electromagnetic radiation or interference.

It is important to note that all electrical equipment, including geothermal systems, generates some level of electromagnetic interference, but these levels are typically well within safe limits and do not pose a significant risk to human health or the environment. If you have concerns about electromagnetic interference from your geothermal system, you can work with a licensed and experienced contractor to assess the system and make any necessary modifications to ensure that it operates safely and efficiently.

Are inverters needed to convert DC to AC with geothermal systems?

Inverters are not typically needed with geothermal systems. Geothermal systems work by tapping into the heat stored in the earth to provide heating, cooling, and hot water for a home. Unlike solar panels, which generate electricity from the sun, geothermal systems do not generate electricity and do not require inverters to convert DC to AC.

Instead, geothermal systems use a heat pump to transfer heat from the earth to the home, where it is used to provide heating, cooling, and hot water. The heat pump operates using electrical power, but it does not generate electricity and, therefore, does not require an inverter.

If you are interested in using geothermal energy to power your home, it is important to work with a licensed and experienced contractor who can help you assess your specific energy needs and determine the best type of geothermal system for your home. They can also provide information on any additional equipment or components that may be needed to ensure the safe and efficient operation of your geothermal system.

Does the heat pump use a Variable Frequency Drive?

Yes, some geothermal heat pumps use a Variable Frequency Drive (VFD) to control the speed of the system's compressor and circulate refrigerant. The VFD helps to regulate the flow of refrigerant, which in turn helps to optimize the efficiency of the heat pump and reduce energy consumption.

VFDs can also be used to control the speed of the system's fan or pump, depending on the specific design of the heat pump. By using a VFD, the heat pump can operate at an optimal speed to meet the demands of the heating and cooling system, which can help to improve efficiency and reduce energy consumption.

It is important to note that not all geothermal heat pumps use a VFD, and the use of a VFD is dependent on the specific design of the heat pump. If you are interested in using a geothermal heat pump with a VFD, it is recommended that you work with a licensed and experienced contractor who can provide information on the specific heat pump and assist with the installation and operation of the system.

Does the VFD produce EMI?

Variable Frequency Drives (VFDs) can produce Electromagnetic Interference (EMI). EMI is the result of electrical and magnetic fields that are generated by electrical equipment and can interfere with other electronic equipment or devices.

In the case of VFDs, the fast switching of the power electronics within the VFD can generate EMI, which can affect other electronic equipment or devices in the vicinity. However, most VFDs are designed with EMI filtering to reduce the level of interference, and modern VFDs are typically well within the limits established by international standards for EMI.

If you are concerned about the potential for EMI from a VFD in your geothermal heat pump system, it is recommended that you work with an experienced EMI Consultant who can assess the specific VFD and make any necessary modifications to ensure that it operates safely and efficiently. They can also provide information on any additional equipment or components that may be needed to reduce the level of EMI from the VFD.

What are the typical frequencies of variable Frequency Drives for geothermal heat pumps?

The typical frequency range for a Variable Frequency Drive (VFD) in a geothermal heat pump system is between 0 and 60 Hertz (Hz). The exact frequency range of a VFD will depend on the specific design and requirements of the geothermal heat pump system.

The VFD is used to control the speed of the system's compressor or fan, which helps to regulate the flow of refrigerant or air within the heat pump. By adjusting the frequency of the VFD, the speed of the compressor or fan can be increased or decreased as needed, which in turn helps to optimize the performance of the heat pump.

It is important to note that different geothermal heat pump systems may use VFDs with different frequency ranges, and the frequency range of the VFD will depend on the specific design of the heat pump system. If you are interested in using a geothermal heat pump with a VFD, it is recommended that you work with a licensed and experienced contractor who can provide information on the specific VFD and assist with the installation and operation of the system.

Solar Power Inverters and EMI Filtering Techniques; Everything You Need to Know

Whether you are an electrical engineer, an electrician, or a homeowner considering a new solar power system installation, or you already own one, you will eventually need to deal with the resultant electromagnetic interference, EMI.

Regardless of the term you prefer, Signal-to-Noise Ratio (S/N or SNR), THD+N (Total Harmonic Distortion Plus Noise), harmonic transients, ripple, or “dirty electricity,” solar systems emit high amplitudes of transient harmonic voltages from semiconductor switching onto an electrical system, often interfering to varying degrees with the function of your appliances, electrical devices, electronics, and, eventually onto you.

(The basic physics formulas that describe this process are: Δv/Δτ and Δi/Δτ, where Δ = change, τ = time interval, v = voltage differences, i = current differences.)

Alternative energy is now more popular than ever, and there is much to learn. In the next few months, I plan to share essential knowledge about each type and how to mitigate the electromagnetic interference they produce.

Solar Power is by far the alternative energy source most often asked about. Solar panels produce direct current (DC) electricity, which is incompatible with the alternating current (AC) electricity used in homes. To use the electricity produced by solar panels, it must be converted from DC to AC.

Here is the basic process to convert solar energy into usable AC electricity for a home:

1. Sunlight: The sun provides the energy source for the solar photovoltaic cells.

2. Solar Photovoltaic Cells: The photovoltaic cells within a series of photovoltaic (PV) panels are installed on the roof or in a suitable location with unobstructed access to sunlight. The panels convert the sunlight into direct current (DC) electricity.

3. DC to AC Inverter: The DC electricity from the panels is sent to a solar inverter, which converts the DC electricity into alternating current (AC) electricity. The inverter is typically located near the electrical service panel in the home.

4. Electrical Service Panel: The AC electricity is then sent to the home's electrical service panel, which is then distributed to the various electrical branch circuits in the home.

5. Energy Metering: A bi-directional meter is installed to monitor the flow of electricity between the home and the electrical grid. This meter allows the homeowner to determine how much electricity is being produced by the solar panels and how much is being drawn from the grid.

6. Electrical Grid Connection: The home is connected to the electrical grid through a power company-owned utility line. This allows the home to receive electricity from the grid when the demand exceeds the supply from the solar panels and to send excess electricity back to the grid when the panels are producing more electricity than the home is using.

7. ESS: (Energy Storage System) is a device that stores excess energy generated by a solar power system. The stored energy can be used later to meet the energy demand when the solar panels are not producing enough energy (e.g., during nighttime or cloudy conditions). An ESS typically consists of batteries or other energy storage technologies and may include power electronics and control systems. Using an ESS can increase the overall efficiency of a solar power system and provide a more reliable and stable energy supply.

   Some popular brands and models of ESS for home use:

   • Tesla Powerwall: This is a lithium-ion battery system designed for residential use and is one of the most well-known ESSs on the market.

   • LG Chem RESU: This is a high-capacity lithium-ion battery system compatible with a wide range of inverters and can be easily integrated into a home solar power system.

   • Sonnen: Sonnen offers several ESS models for residential use, including the SonnenBatterie and the SonnenCore. These systems are designed to work in tandem with solar panels and provide energy storage and backup power.

   • Enphase Energy Storage System: This is a modular battery system that can be added to an existing Enphase solar power system. It uses lithium-ion batteries and has a scalable design, making it suitable for homes of different sizes.

   These are just a few examples of ESSs that are available for residential use. When choosing an ESS for your home, it's important to consider factors such as capacity, compatibility with your existing solar power system, and the local regulations and incentives for energy storage.

(A licensed electrical contractor should be consulted for a detailed design and installation to ensure compliance with local codes and standards.)

The conversion process is accomplished by using an inverter. An inverter takes the DC electricity from the solar panels and converts it into AC electricity. The inverter is usually installed near the solar panels and is connected to the panels through cables. The DC electricity from the panels flows into the inverter and is then converted into AC electricity.

When choosing an inverter, it is important to consider the following factors:

1. Power capacity: The inverter must have the capacity to handle the amount of electricity produced by the solar panels.

2. Efficiency: An efficient inverter will produce less heat and more efficiently convert DC to AC electricity.

3. Grid compatibility: Inverters are designed to be compatible with the electrical grid in your area. It is important to choose an inverter that is compatible with your local electrical grid.

4. Size: The inverter must be appropriately sized for the amount of electricity produced by the solar panels.

By converting DC solar to AC electricity, homes can use the clean and renewable energy produced by their solar panels to power their homes. This not only reduces their carbon footprint but also saves on electricity costs.

Reducing line noise or Electromagnetic Interference (EMI) is integral to the DC-to-AC conversion process.

Here are a few steps that can be taken to reduce EMI:

1. Proper grounding: Ensure that the inverter is properly grounded to minimize the risk of EMI.

2. Quality components: Use high-quality components in the inverter circuit to reduce EMI.

3. Shielding: Shield the inverter and cables with metal casing or braided shielding to reduce the emission of EMI.

4. Ferrite beads: Place ferrite beads on the DC and AC cables to absorb EMI.

5. Filtering: Implement appropriate filtering in the inverter circuit to reduce EMI.

6. Proper installation of the inverter and cables will also reduce EMI.

Reducing EMI is important to ensure that the electrical system remains stable and does not interfere with other electrical equipment. By taking these steps, you can reduce the risk of EMI and ensure that your DC to AC-conversion process is efficient and reliable.

Here are a few EMI filters commonly used in DC to AC conversion applications:

• Common-Mode Choke: A common-mode choke is a type of inductor placed on the DC and AC cables to absorb EMI. It is typically used in pairs, one placed on the positive line and one on the negative line, to reduce the common-mode noise on both lines. The choke consists of a wire coil wound around a magnetic core. The magnetic core is designed to increase the coil's inductance, which helps reduce the flow of high-frequency noise.

  A common-mode choke provides a low impedance path for the common-mode noise, which helps reduce the amount of noise transmitted from the power source to the equipment. The choke acts as a filter, absorbing the high-frequency noise and reducing the amount of EMI in the system.

  Common-mode chokes are a simple, effective, and reliable solution for reducing EMI in electrical systems and are widely used in various applications, such as DC to AC power inverters, power supplies, and motor drives. They are particularly useful in applications with high common-mode noise, providing a cost-effective solution for reducing this noise.

• Pi Filter: A Pi filter is a type of LC filter placed on the AC output of the inverter to reduce EMI. It is a passive circuit that consists of two inductors (L) and two capacitors (C) arranged in a Pi configuration.

  The Pi filter works by reducing high-frequency noise in the system. The inductors act as choke coils, limiting the flow of high-frequency noise, while the capacitors act as bypasses, short-circuiting the high-frequency noise and passing it to ground.

  The Pi filter is often used in applications where the requirement for EMI reduction is high, such as in DC to AC power inverters, power supplies, and motor drives. The Pi filter can be customized to meet the application's specific requirements, such as the frequency range and the level of EMI reduction required.

  The Pi filter is a simple, cost-effective, and reliable solution for reducing EMI in electronic systems. It is widely used in various applications and is considered a standard solution for EMI reduction.

• Common-Mode Filter: A common-mode filter is a type of filter that is placed on the AC output of the inverter to reduce EMI. A common-mode filter is an EMI (Electromagnetic Interference) filter used to suppress common-mode noise in electrical systems. It works by suppressing the differential-mode noise and passing the common-mode noise through capacitors and inductors.

  The components of a common-mode filter include:

  • Chokes (Inductors): These components limit the flow of high-frequency noise.

  • Capacitors: These components provide a low-impedance path to ground for high-frequency noise.

  • Ferrite Beads: These components act as high-frequency low-pass filters and provide additional EMI suppression.

  The common-mode filter is connected in parallel with the power or signal lines to be protected, with the positive side connected to one line and the negative side connected to the other line. The combination of inductors and capacitors in the filter creates a low-impedance path for common-mode noise, effectively filtering it out of the signal.

• Line Filter: A line filter is an EMI filter placed on the AC input of the inverter to reduce EMI. These filters can be selected based on the specific requirements of the application, such as the amount of EMI reduction required, the type of electrical equipment that needs to be protected, and the cost and availability of the filters. Usually, a combination of these filters is used to achieve the desired level of EMI reduction.

  A line filter is typically placed between the power source and the equipment being powered to reduce the amount of high-frequency noise transmitted from the power source to the equipment. Line filters are an effective and reliable solution for reducing EMI in electrical systems and are widely used in various applications.

A typical Line Filter consists of the following components:

1. Inductor(s): One or more inductors are used to limit the flow of high-frequency noise, which acts as a choke coil.

2. Capacitor(s): One or more capacitors are used to short-circuit the high-frequency noise, which acts as a bypass.

3. Resistor(s): One or more resistors are used to provide damping to the filter, which helps to reduce ringing and overshoot.

4. Metal casing: The components are housed in a metal casing to provide shielding and to reduce the emission of EMI.

The number and values of the components can vary depending on the application's specific requirements, such as the frequency range and the level of EMI reduction required. Line filters can also be designed to meet specific equipment requirements, such as motor drives, power supplies, and DC to AC inverters.

• Differential-Mode Filter: A differential-mode filter is placed on the DC input of the inverter to reduce EMI. A differential-mode filter is another EMI (Electromagnetic Interference) filter that reduces noise in electrical systems. It is designed to reduce the differential-mode noise between two lines, such as the positive and negative lines in a power supply.

  A Differential-Mode Filter typically consists of the following components:

  1. Inductor(s): One or more inductors are used to limit the flow of high-frequency noise, which acts as a choke coil.

  2. Capacitor(s): One or more capacitors are used to short-circuit the high-frequency noise, which acts as a bypass.

  3. Resistor(s): One or more resistors dampen the filter, which helps reduce ringing and overshoot.

  Again, the number and values of the components can vary depending on the application's specific requirements, such as the frequency range and the level of EMI reduction required. The inductors limit the flow of high-frequency noise, while the capacitors short-circuit the high-frequency noise and pass it to ground. The resistors provide damping, which helps to reduce ringing and overshoot.

There are several types of inverters used to convert DC to AC, including:

1. Square Wave Inverter: generates a square wave output with abrupt transitions between the positive and negative voltages.

   Advantages: Simple design, low cost.

   Disadvantages: Poor power quality, increased harmonic distortion, inefficient operation of some electrical devices.

2. Modified Sine Wave Inverter: generates a waveform that approximates a sine wave, with smoother transitions than a square wave.

   Advantages: Improved power quality compared to a square wave inverter and lower cost compared to a pure sine wave inverter.

   Disadvantages: Still inferior power quality compared to a pure sine wave inverter, increased harmonic distortion.

3. Pure Sine Wave Inverter: generates a waveform that is a close representation of a true sine wave.

   Advantages: High power quality, efficient operation of all electrical devices, low harmonic distortion.

   Disadvantages: More complex and expensive design compared to other types.

4. Pulse Width Modulation (PWM) Inverter: uses digital signals to generate an AC output by switching the DC voltage on and off at a high frequency.

   Advantages: High power quality, high efficiency, and low harmonic distortion.

   Disadvantages: Complex design, the higher cost compared to other types.

A Pulse Width Modulation (PWM) Inverter typically consists of the following components:

1. DC source (e.g. battery)

2. Power electronic switches (e.g. MOSFETs, IGBTs)

3. Inductor or transformer

4. Capacitor

5. Control circuit (e.g. microcontroller, gate driver circuit)

6. Protection circuit (e.g. over-voltage, over-current)

7. Output filter to smooth the PWM waveform into a sinusoidal waveform.

A MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor): is a power electronic switch that controls the flow of electric current by using an electric field. MOSFETs are widely used in inverters due to their fast switching speeds, high efficiency, and simple drive requirements. (More info on MOSFETs in the Addendum.)

An IGBT (Insulated-Gate Bipolar Transistor): is another power electronic switch that combines the benefits of a bipolar transistor and a MOSFET. IGBTs are capable of handling high current and voltage levels, and they have fast switching speeds like MOSFETs. This makes them ideal for high-power inverter applications where high efficiency and high power density are desired. (More info on IGBTs is in the Addendum.)

The Protection Circuit in a PWM inverter is designed to prevent damage to the inverter components and to ensure the safe operation of the system. Protection circuits are typically used to detect and respond to over-voltage, over-current, short-circuit, and thermal conditions.

1. Over-Voltage Protection: Detects and responds to high voltage levels in the inverter output, which can damage the components or cause safety issues.

2. Over-Current Protection: Detects and responds to high current levels in the inverter output, which can cause overheating and damage to the components.

3. Short-Circuit Protection: Detects and responds to a short-circuit condition in the inverter output, which can cause high current levels and damage the components.

4. Thermal Protection: Detects and responds to high-temperature levels in the inverter components, which can cause overheating and permanent damage.

When these protection events occur, the protection circuit typically shuts down the inverter operation or reduces the output power to prevent further damage. The protection circuit is an important component in ensuring the safe and reliable operation of the PWM inverter.

In a Pulse Width Modulation (PWM) inverter, the type of capacitor is typically an electrolytic capacitor. These capacitors are used in the output filter circuit to smooth the PWM waveform into a sinusoidal waveform. The capacitance value and voltage rating of the capacitor depending on the power rating and operating conditions of the inverter.

Electrolytic capacitors are preferred for PWM inverters because of their high capacitance density and relatively low cost. Additionally, electrolytic capacitors have a relatively low equivalent series resistance (ESR), which is important for reducing switching losses and improving the overall efficiency of the inverter.

Other types of capacitors, such as tantalum capacitors, may also be used in PWM inverters. However, these capacitors are typically more expensive and have lower capacitance density than electrolytic ones.

In a Pulse Width Modulation (PWM) inverter, the type of transformer is typically an isolation transformer. The purpose of the isolation transformer is to provide electrical isolation between the input DC voltage and the output AC voltage.

The isolation transformer serves several important functions in the PWM inverter, including:

1. Reducing the voltage stress on the power electronic switches.

2. Improving the safety of the inverter by preventing electrical shock and fire hazards.

3. Reducing electromagnetic interference (EMI) generated by the inverter.

Isolation transformers are designed with specific characteristics based on the power rating and operating conditions of the inverter. The primary winding is connected to the input DC voltage, while the secondary winding is connected to the output AC voltage. The transformer's turn ratio is designed to step up or down the voltage to the desired level.

The isolation transformer is an important component in ensuring the reliability and performance of the PWM inverter.

A Pulse Width Modulation (PWM) inverter typically uses an LC (Inductor-Capacitor) output filter to smooth the PWM waveform into a sinusoidal waveform. The LC filter consists of an inductor and a capacitor connected in series or parallel. The LC filter is designed to reduce the harmonic content of the PWM waveform by filtering out high-frequency components and passing the desired sinusoidal waveform.

The LC Filter removes high-frequency harmonic content from the output waveform of the inverter, resulting in a smoother, more sinusoidal waveform. The inductors store energy and block the high-frequency harmonics, while the capacitors serve to smooth the waveform and prevent high-frequency oscillations.

The type of LC filter used in a PWM inverter depends on the power rating, operating frequency, and other specifications of the inverter. The LC filter components are selected based on their frequency response, impedance, and stability characteristics.

The LC filter is an important component in ensuring the performance and efficiency of the PWM inverter by improving the waveform quality and reducing harmonic distortion.

Examples of LC filters used in PWM inverters include:

1. Series LC Filter is a type of output filter used in power electronics to smooth and shape the output waveform of a power inverter. It comprises an inductor (L) and a capacitor (C) connected in series.

   A series LC filter is a simple and effective way to improve the waveform quality of a power inverter. However, it may not be as effective in removing high-frequency harmonics as a more complex filter, such as a cascaded LC filter or a Pi filter.

   Series LC filters are commonly used in low-power applications where a simple, low-cost solution is desired, such as small inverters or battery chargers.

2. Parallel LC Filter is a type of output filter used in power electronics to smooth and shape the output waveform of a power inverter. It comprises an inductor (L) and a capacitor (C) connected in parallel.

   The LC filter removes high-frequency harmonic content from the output waveform of the inverter, resulting in a smoother, more sinusoidal waveform. The inductor blocks high-frequency harmonics and the capacitor serves to smooth the waveform and prevent high-frequency oscillations.

   A parallel LC filter is a simple and effective way to improve the waveform quality of a power inverter. A parallel filter may not be as effective in removing high-frequency harmonics as a more complex filter, such as a series LC filter or a Pi filter.

   Parallel LC filters are commonly used in low-power applications where a simple, low-cost solution is desired, such as small inverters or battery chargers.

3. Cascaded LC Filter is a type of output filter used in power electronics to smooth and shape the output waveform of a power inverter. It is comprised of multiple stages of inductors (L) and capacitors (C) connected in series, hence the name "cascaded LC filter."

   In a cascaded LC filter, multiple stages of LC components are used to filter the output waveform better. This improves the waveform quality, reduces harmonic distortion, and improves the power inverter's overall efficiency and reliability.

   Cascaded LC filters are commonly used in applications that require a clean and stable output waveform, such as uninterruptible power supplies (UPS), renewable energy systems, and motor drives.

A Pure Sine Wave Inverter consists of the following components:

1. DC-AC Converter: Converts the input DC voltage into a sinusoidal AC voltage.

2. Output Filter: Smooths the AC waveform and reduces harmonic content.

3. Control Circuit: Regulates the output voltage and frequency and monitors the inverter for protection events.

The DC-AC Converter in a pure sine wave inverter typically uses the carrier-based pulse width modulation (PWM) technique. This technique converts the DC voltage into a high-frequency sinusoidal waveform, filtered and amplified to produce the desired AC voltage.

A Pure Sine Wave Inverter is a type of inverter that converts direct current (DC) into a sinusoidal alternating current (AC) waveform. Unlike a Pulse Width Modulation (PWM) inverter, which generates a square waveform that resembles a sinusoidal waveform, a pure sine wave inverter generates a true sinusoidal virtually indistinguishable from a utility-supplied AC waveform.

Compared to a PWM inverter, a pure sine wave inverter typically has a more complex control circuit and requires more sophisticated components, such as high-frequency power transistors and specialized output filters. However, the output waveform quality of a pure sine wave inverter is significantly better than that of a PWM inverter, making it suitable for applications that require a clean, reliable power source.

In addition to its improved waveform quality, a pure sine wave inverter provides improved efficiency, reduced noise, EMI, and better compatibility with sensitive loads, such as computers and audio equipment.

Some popular brands and models of Pure Sine Wave Inverters include:

1. Victron Energy Phoenix Inverters

2. Outback Power FlexMax Inverters

3. Xantrex Freedom Inverters

4. Schneider Electric XW Inverters

5. SMA Sunny Boy Inverters

6. EcoFlow Delta Inverter Generators

7. Inverter Generators by Yamaha and Honda

These brands and models offer a range of power ratings and features, including compact design, high efficiency, low noise, and remote monitoring capabilities. These inverters are widely used in various applications, including off-grid and mobile power systems, backup power, and commercial and industrial power solutions. The specific model and brand will depend on the user's requirements and application.

Some popular brands and models of Pulse Width Modulation (PWM) inverters include:

1. PowerBright PW1100-12

2. KRIËGER 1100 Watt 12V Power Inverter

3. Energizer EN1100

4. AMPEAK 1000W Power Inverter

5. BESTEK 500W Power Inverter

6. Go Power! GP-SW1000-12

7. AIMS Power PWRI110012

These brands and models offer a range of power ratings and features, including compact design, high efficiency, low noise, and remote monitoring capabilities. These inverters are widely used in various applications, including off-grid and mobile power systems, backup power, and commercial and industrial power solutions. The specific model and brand will depend on the user's requirements and application.

Pi Filter Diagram © 2023

Addendum:

1. The Pi Filter is a type of output filter used in power electronics to smooth and shape the output waveform of a power inverter. It gets its name from its shape, which resembles the Greek letter "π" and consists of two inductors (L) and a capacitor (C) connected in a specific arrangement. The inductors block high-frequency harmonics, while the capacitor serves to smooth the waveform and prevent high-frequency oscillations.

In the diagram, L1 and L2 represent the inductors, and C1 represents the capacitor. The inductors are connected in series, with their common connection connected to the capacitor. The other terminal of L1 is connected to the inverter output, while the other terminal of L2 is connected to ground. The other terminal of the capacitor is also connected to the inverter output.

The topology of a Pi filter can be represented as follows: two inductors are connected in series, with the common connection of the two inductors being connected to a capacitor. The other terminal of the first inductor and the other terminal of the capacitor is connected to the inverter output. In contrast, the other terminal of the second inductor is connected to ground.

The Pi filter is a more complex and effective filter than a series LC filter or a parallel LC filter. It is commonly used in applications that require a clean and stable output waveform, such as uninterruptible power supplies (UPS), renewable energy systems, and motor drives.

MOSFET Diagram © 2023

2. The operation of the MOSFET is based on the flow of charge carriers (electrons or holes) through a channel between the source and the drain, which is controlled by the voltage applied to the gate terminal. The gate terminal is insulated from the channel and is connected to the body, allowing the charge carriers to flow between the source and drain.

When a positive voltage is applied to the gate terminal, it attracts electrons and forms an inversion layer in the channel, which enhances the conductivity between the source and drain. When a negative voltage is applied to the gate terminal, it repels electrons and reduces the conductivity between the source and drain.

MOSFETs are widely used in power electronics due to their high input impedance, fast switching speed, and low on-state resistance, making them ideal for high-frequency switching applications, such as PWM inverters.

Here is a diagram that represents the basic structure of a MOSFET. In the diagram, the MOSFET has three terminals: the source (S), the drain (D), and the body (B). The source and drain form the input/output of the MOSFET, while the body is connected to the substrate or the source.

IGBT diagram © 2023

3. IGBTs are widely used in power electronics due to their high voltage and current capabilities, fast switching speed, and low on-state voltage drop, making them ideal for high-power switching applications, such as PWM inverters and UPS systems.

The operation of the IGBT is based on the flow of charge carriers (holes and electrons) between the emitter and collector, which is controlled by the voltage applied to the base terminal. When a positive voltage is applied to the base terminal, it causes holes to flow from the emitter to the base, creating a high current flow from the collector to the emitter, turning on the IGBT. When the voltage is removed from the base, the holes stop flowing, turning off the IGBT.

Here is a diagram that represents the basic structure of an IGBT. In the diagram, the IGBT has three terminals: the emitter (E), the collector (C), and the base (B). The emitter and collector form the input/output of the IGBT, while the base is connected to the p-n junction of the device.

What are the potential long-term drawbacks of using solar power for a home?

Here are some potential long-term drawbacks of using solar power for a home:

1. Initial Costs: Installing a solar energy system can be expensive, ranging from $10,000 to $30,000. This may make it less accessible for some homeowners, especially those on a tight budget.

2. Maintenance: Solar panels require regular cleaning and maintenance to maintain their efficiency. This may require homeowners to invest time and money into keeping their systems in good working order.

3. Location Dependency: The efficiency of solar panels can be affected by weather conditions, such as cloud cover, dust, and other environmental factors. This means that homeowners may experience reduced energy generation during inclement weather.

4. Energy Storage: Solar panels generate electricity during daylight hours but may not generate enough energy to meet the needs of a home during periods of low light or at night. This means that homeowners may need to invest in energy storage systems, such as batteries, to ensure that they have a reliable energy source when needed.

5. Incompatible with Older Homes: Solar panels may not be suitable for older homes with limited roof space or outdated electrical systems and may require homeowners to make significant upgrades to accommodate the technology.

6. Interference with Other Technologies (if you do not preemptively remediate EMI): Solar panels may interfere with other technologies, such as radio or television signals, or cause electromagnetic interference. This may result in performance issues or other problems that can be difficult and expensive to resolve.

It is important to note that these potential drawbacks will vary depending on the specific system, location, and other factors. Before choosing a solar energy system, it is important to carefully consider the costs, benefits, and potential drawbacks of the technology and to work with a licensed and experienced contractor to ensure the quality and safety of your installation.

What are the long-term benefits of using solar power for a home?

Here are some long-term benefits of using solar power for a home:

1. Cost Savings: By generating their electricity, homeowners who use solar power can reduce their dependence on traditional energy sources, such as the grid, and save money on energy bills over time.

2. Energy Independence: Solar power systems allow homeowners to generate their electricity, making them less dependent on traditional energy sources, such as the grid. This can provide greater energy security, especially in areas where power outages are common.

3. Environmentally Friendly: Solar power is a clean and renewable energy source that produces no emissions or pollution. This makes it an environmentally friendly option for homeowners who want to reduce their carbon footprint.

4. Low Maintenance: Solar panels are low maintenance and require minimal cleaning and upkeep, making them a hassle-free option for homeowners who want to generate their electricity.

5. Increase Property Value: Homes equipped with solar power systems are often seen as more valuable and appealing to potential buyers, which can increase the property's value over time.

6. Federal and State Incentives: There are federal and state tax credits, rebates, and other incentives available for homeowners who install solar power systems, which can help offset the initial costs of installation and make the technology more accessible.

It is important to note that the specific benefits of using solar power to electric power a home will depend on the specific system, location, and other factors. Before choosing a solar energy system, it is important to carefully consider the costs, benefits, and potential drawbacks of the technology and to work with a licensed and experienced contractor to ensure the quality and safety of your installation.

© 2023. All rights are reserved.

EMF Testing Meters: Professional vs. Amateur

The AlphaLab Inc. UHS2, costing nearly $400, is a good amateur and semi-pro meter for measuring AC magnetic fields. It can be NIST-certified as a reference meter by AlphaLab Inc.

EMF Testing for health has become increasingly popular around the world. Several retail companies such as Safe Living Technologies, LessEMF, Amazon, Grainger, and others sell consumer-level (amateur) meters, which are easy to use for obtaining a general sense of one’s exposure.

These meters can range from $150 to about $2,000. Should you buy one?

The answer is: yes, and no. It depends on your needs.

If you want a general sense of whether you are moving closer or further from a strong field your meter is designed to measure, then yes. The numbers you read on the meter will only be a reference to compare with other readings you have taken, but the meter will help you learn.

Most consumer-level meters tend not to be accurate at all. Many can not be calibrated. Some “manufacturer-calibrated” meters tend not to hold their calibration very long. Their calibrations certainly will not last one year. This quality of meters can provide readings ranging from 2-20 times higher or lower than the actual amplitudes.

Some more expensive manufacturer-calibrated meters can hold their original calibration for several years, such as the Gigahertz Solutions meters used by many of the members of the Building Biology® Institute. (Note: We have not yet found an ISO 9001 calibration lab in the USA that can provide an ISO 17025 calibration for the Gigahertz Solutions NFA1000. Consequently, we can only use these excellent Near-Field Analyzers in limited applications. We use higher-tier professional equipment for verifiable measurements required in official reports.)

Suppose you need numbers to send your building manager, local power company, town board, or anyone else you need to take action. In that case, a manufacturer-calibrated meter will not be sufficient. (But, even if you had a professional meter, it could still provide inaccurate results unless you are appropriately trained to use it and know how to measure and assess an electromagnetic field correctly.)

So, what is a professional EMF meter?

Well, here again, it depends on your needs. If you are taking general measurements to provide some remediation, a NIST (National Institute of Standards) certified-calibrated meter will ensure that your meter is accurate enough to use as a reference. This means that your meter was compared to another one that was traceable to a NIST-calibrated meter. The meter used to calibrate your meter may not have been the original NIST calibrated meter, and that original meter may no longer be NIST calibrated either. This is why you must ensure your meter is NIST-certified by an ISO 17025 or ISO 9001 lab.

These ISO 17025 and 9001 labs are inspected annually, and their calibration tools are tested and calibrated by a licensed inspector. The people calibrating your meters are also vetted and approved as competent.

So, now, is your meter a professional meter?

Perhaps, but not necessarily for all needs.

Suppose you need measurements that demand professional-level accuracy for replicable studies, verifiable reports, and high-risk measurements. In that case, you need an accredited ANSI/NCSL Z540-1 or ISO 17025 certified-calibrated tool.

And, if you need readings to send to your building manager, condo board, local power company, township trustees, science or engineering staff, or anyone else whom you need to appeal for action, then you will need a meter certified-calibrated to the ISO 17025 standard and hire someone who can measure correctly and submit a bullet-proof report.

The difference between a NIST-certified reference meter and an ISO 17025 or ANSI/NCSL Z540-1 certification, other than the ensured quality of the calibration lab, is the rigorous and detailed level of testing these meters undergo and the detail of the certification testing reported results. These reports will provide accuracy at either dB +/- or the percentage of accuracy for each frequency the tool is calibrated and/or the levels of power it measured at these frequencies.

Depending on the build quality, functional capabilities, and accuracy, professional meters like those we use at Elexana cost ten-of-thousands of dollars each. And, each year, we spend well beyond $10,000 in calibration costs.

Suppose you intend to hire an “expert” to provide you with professional-level numbers. In that case, you need someone who is properly trained to measure, has several years of measuring experience and brings ANSI/NCSL Z540-1 or ISO 17025 certified-calibrated equipment with up-to-date certificates.

ANSI, IEEE, ISO/IEC, CISPR, EN, CEN, CENELEC, and ETSI standards recommend up-to-date certified-calibrated certificates included within final reports or made available upon request, or your report may not be counted on for accuracy; therefore, rendered as unreliable. The report would certainly not hold up for accreditation or verifiability.

© 2022 All rights are reserved.