Solar-assisted Heat Pumps: [Ultimate Guide]
Heat pumps are a cost-effective alternative to traditional heating and cooling systems, but they can be even more efficient when paired with solar panels.
Because solar-assisted heat pumps use solar energy to help power the pump, they can reduce your reliance on grid-supplied electricity, saving you money on your energy bills.
A heat pump's primary function is to take the heat from one place and move it to another.
That is why heat pumps work similarly to a refrigerator. However, a refrigerator can move heat in one direction only from the inside of the fridge to the outside.
While a heat pump can work in both directions. It can take heat from the ground or air and pump it into your home.
And it can also take heat from your home and release it into the ground or air outside. In this way, it can provide both heating and cooling for your home.
Modern heat pump systems can deliver three or four times as much thermal energy in the form of heat as they consume in electrical energy to operate.
This is possible due to the higher efficiency of the compressors and motors used in heat pumps, as well as advances in refrigerant technology.
A heat pump is still isn't a self-sufficient heating and cooling system. It typically needs the grid energy to circulate the refrigerant that helps transfer the heat.
However, solar-assisted heat pumps (or solar-powered heat pumps) take advantage of solar panels to help offset the electricity needed to power the system.
These systems can offset a considerable amount of your energy consumption, potentially saving you money on your utility bills.
What are solar-assisted heat pumps?
Solar-assisted heat pumps (SAHPs) are not a new technology; they were first developed in the 1970s.
The first SAHPs were installed in Europe and Japan. In recent years, there has been an increased interest in solar-assisted heat pumps in the United States.
A solar-assisted heat pump (SAHP) is also known as a “solar-powered heat pump” or a “solar heat pump system”. It is a machine that combines two technologies: the solar panel, which captures energy from the sun, and the heat pump, which uses that energy to heat or cool a space.
SAHP uses the sun's energy to heat the refrigerant that circulates through the heat pump. This helps offset the electricity needed to power the system and can make the heat pump more efficient.
In this system, the solar thermal panel serves as a low-temperature heat source to power the heat pump's evaporator.
The goal of this system is to achieve a high COP while producing energy more efficiently and at a lower cost than a traditional grid-tied heat pump.
SAHPs are becoming more efficient and cost-effective as technology advances. They are a greener alternative to traditional heating and cooling systems that can reduce or eliminate the need for grid-supplied electricity to condition spaces.
How do solar-assisted heat pumps work?
Solar-assisted heat pumps work by using the sun's energy to heat a fluid, which is then used to power the heat pump. The solar thermal panel captures energy from the sun and transfers it to the fluid.
The fluid then circulates through the heat pump's evaporator, where it transfers its heat to the refrigerant. The refrigerant then circulates through the heat pump's compressor, where it transfers the heat to the air or ground outside.
The solar panel does not generate electricity; it only captures the sun's energy and transfers it to the fluid. The heat pump uses this fluid to generate electricity, which powers the system.
SAHPs are not 100% solar-powered. They still need grid-supplied electricity to operate.
However, the solar panel helps offset the electricity needed to power the system, making it more efficient. If the sun's energy is not sufficient, the system will automatically switch to grid-supplied electricity as a backup.
The reason why SAHPs cannot be 100% solar-powered is that the heat pump's compressor needs a source of electricity to run. The compressor is what circulates the refrigerant through the system.
The compressor is the most energy-intensive part of the heat pump, and it needs a constant supply of electricity to run. The solar panel can only provide a portion of the electricity needed to run the compressor; the rest must come from the grid.
Powering a heat pump completely with solar power is possible, but the system would need to be much larger, sophisticated, and more expensive.
This type of system would also require a battery to store the solar energy for use at night or during cloudy days.
What are the components of a solar-assisted heat pump system?
A solar-assisted heat pump system has four main components:
Solar Thermal Panel
Solar thermal panels are also known as “solar collectors” since they collect solar energy. They capture energy from the sun and transfer it to the fluid.
They are typically built as a flat panel that serves as a low-temperature heat source for the heat pump. The size of the solar thermal panel depends on the size of the heat pump and the amount of solar energy available.
The solar collector can be mounted on the roof or on the ground. Depending on the type of system, the solar collector may be a flat-plate collector or an evacuated tube collector.
Flat-plate collectors
Flat-plate collectors are the most common type of solar collector. They consist of a metal plate that is coated with a material that absorbs the sun's energy, such as copper or aluminum. The plate is then enclosed in an insulated box.
The heat from the plate is transferred to the fluid in the coil by conduction and convection. The fluid in the coil then transfers the heat to the heat pump.
Advantages of flat-plate collectors:
- They are less expensive than evacuated tube collectors.
- They are easier to install.
- They can be used in a wider range of climates.
Disadvantages of flat-plate collectors:
- They are less efficient than evacuated tube collectors.
- They can be damaged by hail or high winds.
Evacuated tube collectors
Evacuated tube collectors are less common than flat-plate collectors, but they are more efficient.
They consist of a series of tubes that are coated with a material that absorbs the sun's energy, such as copper or aluminum. The tubes are then enclosed in an evacuated (sealed) glass container.
The heat from the sun is transferred to the fluid in the coil by conduction and convection. The fluid in the coil then transfers the heat to the heat pump.
Advantages of evacuated tube collectors:
- More efficient than flat-plate collectors
- Can be used in colder climates
- Can be used in areas with high winds
- Can be used in areas with high dust levels
Disadvantages of evacuated tube collectors:
- More expensive than flat-plate collectors
- More difficult to install
Heat Pump
The heat pump uses the fluid from the solar thermal panel to generate electricity, which powers the system.
The heat pump has an evaporator, which transfers heat from the fluid to the refrigerant. The refrigerant then circulates through the heat pump's compressor, where it transfers the heat to the air or ground outside.
The heat pump is the most energy-intensive part of the system, and it needs a constant supply of electricity to run.
Air-source heat pump
An air-source heat pump transfers heat between your home and the outside air.
Advantages of air-source heat pumps:
- Inexpensive to install
- Can be used in most climates
Disadvantages of air-source heat pumps:
- Less efficient than ground-source heat pumps
- Can be noisy
Ground-source heat pump
A ground-source heat pump transfers heat between your home and the ground.
Advantages of ground-source heat pumps:
- More efficient than air-source heat pumps
- Can be used in most climates
Disadvantages of ground-source heat pumps:
- More expensive to install
- Requires more space than air-source heat pumps
Water-source heat pump
A water-source heat pump transfers heat between your home and a water source, such as a lake or river.
Advantages of water-source heat pumps:
- Can be used in most climates
- More efficient than air-source heat pumps
Disadvantages of water-source heat pumps:
- More expensive to install
- Requires a water source
Compressor
The compressor circulates the refrigerant through the system. It is the most energy-intensive part of the heat pump and needs a constant supply of electricity to run.
The compressor is typically powered by the grid, but the solar thermal panel can offset some of the electricity needed to run it.
Reciprocating compressor
A reciprocating compressor uses a piston to compress the refrigerant. It is the most common type of compressor used in heat pumps.
Advantages of reciprocating compressors:
- Inexpensive
Disadvantages of reciprocating compressors:
- Less efficient than scroll compressors
- Noisy
Scroll compressor
A scroll compressor uses two intermeshing scrolls to compress the refrigerant.
Advantages of scroll compressors:
- More efficient than reciprocating compressors
- Quieter than reciprocating compressors
Disadvantages of scroll compressors:
- More expensive than reciprocating compressors
- Not as widely available as reciprocating compressors
Refrigerant
The refrigerant is a fluid that transfers heat from the solar panel to the heat pump. It is typically a gas or liquid that evaporates at low temperatures and condenses at high temperatures.
The refrigerant circulates through the heat pump's evaporator, where it transfers its heat to the refrigerant. The refrigerant then circulates through the heat pump's compressor, where it transfers the heat to the air or ground outside.
Types of refrigerants used in heat pumps:
Fluorocarbon refrigerants: Fluorocarbon refrigerants are the most common type of refrigerant used in heat pumps. They are typically used in air-source heat pumps.
HCFC refrigerants: HCFC refrigerants are a type of fluorocarbon refrigerant. They are typically used in ground-source heat pumps.
HCFC refrigerants have been phased out because they contribute to the depletion of the ozone layer. Examples of HCFC refrigerants include R-22 and R-410A.
HFC refrigerants: HFC refrigerants are a type of fluorocarbon refrigerant. They are typically used in water-source heat pumps.
HFC refrigerants are offered for being phased out because they contribute to global warming. Examples of HFC refrigerants include R-134A and R-407C.
CO2 refrigerants: CO2 refrigerants are a type of fluorocarbon refrigerant. They are typically used in ground-source heat pumps.
CO2 refrigerants have a low impact on the environment but aren't as efficient as HCFC or HFC refrigerants. Examples of CO2 refrigerants include R-744 and R-290.
Ammonia refrigerants: Ammonia refrigerants are a type of refrigerant that is not a fluorocarbon.
They are typically used in water-source heat pumps. Ammonia refrigerants are highly flammable and must be handled with care. Examples of ammonia refrigerants include R-717 and R-718.
What are the benefits of solar-assisted heat pumps?
There are several benefits to using solar-assisted heat pumps:
Reduces reliance on the grid
Solar-assisted heat pumps can reduce your reliance on the grid. Because the solar thermal panel offsets some of the electricity needed to run the compressor, you'll use less grid-supplied electricity.
This can help you save money on your electric bill and reduce your carbon footprint.
Improves efficiency
Solar-assisted heat pumps are more efficient than traditional heat pumps. The solar thermal panel preheats the refrigerant, which reduces the amount of energy needed to compress it.
This makes the heat pump more efficient and can help you save money on your energy bill.
Reduces emissions
Solar-assisted heat pumps produce fewer emissions than traditional heat pumps. The solar thermal panel offsets the emissions from the compressor, making the heat pump more environmentally friendly.
Saves money
Solar-assisted heat pumps can save you money on your energy bill. Because they are more efficient than traditional heat pumps, they use less electricity. This can help you save money on your electric bill.
What are the drawbacks of solar-assisted heat pumps?
There are a few drawbacks to using solar-assisted heat pumps:
Initial cost
Solar-assisted heat pumps can be more expensive than traditional heat pumps. The solar thermal panel and installation can add to the upfront cost of the heat pump.
Maintenance
Solar-assisted heat pumps require more maintenance than traditional heat pumps. The solar thermal panel needs to be cleaned and maintained to ensure it is working properly.
Not available in all areas
Solar-assisted heat pumps are not available in all areas. Some areas do not have enough sun to power the solar thermal panel. Other areas do not allow solar thermal panels to be installed.
How do I choose a solar-assisted heat pump?
There are a few things to consider when choosing a solar-assisted heat pump:
Type of refrigerant
The type of refrigerant used in the heat pump will affect its efficiency and environmental impact. HCFC, HFC, and CO2 refrigerants are more efficient than ammonia refrigerants.
However, HCFC and HFC refrigerants contribute to global warming, while CO2 refrigerants have a low impact on the environment.
Size
The size of the solar-assisted heat pump will affect its efficiency. A larger heat pump will allow more heat to be transferred, making it more efficient. However, a larger heat pump will also be more expensive.
Climate
The climate you live in will affect the efficiency of the heat pump. Because the temperature difference between the ground and the air dictates the amount of heat that can be transferred.
The higher the temperature difference, the more efficient the heat pump will be.
Solar thermal panel
The solar thermal panel is an important part of the solar-assisted heat pump.
The panel needs to be the right size to power the heat pump and meet your energy needs. The panel also needs to be properly installed to ensure it is working properly.
What types of solar panels can be used with solar-assisted heat pumps?
Any type of solar thermal panel (sheet and tubes, roll-bond, heat pipe, thermal plates) or hybrid (mono/polycrystalline, thin-film) can be utilized as the solar collector in a solar-assisted heat pump system.
However, the hybrid panel is the preferred type of solar panel for use with ASHPs. Because it allows covering a portion of the heat pump's electricity demand while reducing power consumption and, as a result, the system's costs.
How can solar-assisted heat pumps be made more efficient?
There are a few ways to make your solar-assisted heat pump more efficient:
Use a thermal storage tank
A thermal storage tank can store solar-heated water for use when the sun is not shining. This will help to offset the heat pump's electricity consumption.
Use a higher-efficiency heat pump
A more efficient heat pump will use less electricity and, as a result, will be less expensive to operate.
Use a solar collector with a higher efficiency
The efficiency of the solar collector will affect the amount of heat that is transferred to the fluid in the coil.
A more efficient solar collector will transfer more heat to the fluid, which will help to offset the heat pump's electricity consumption.
Install a solar tracking system
The sun moves across the sky during the day, so a solar tracking system will help to keep the solar collector pointed at the sun. This will maximize the amount of heat that is transferred to the fluid in the coil.
There is almost always some type of compromise when it comes to efficiency.
For example, lowering the evaporation temperature of the refrigerant fluid results in higher thermal efficiency from a solar panel, but a lower performance from the heat pump, which has a lower COP.
Also, heat pumps and other auxiliary boilers that provide power for loads not covered by renewable sources are typically optimized with a focus on reducing their electrical consumption, or the primary energy they consume.
Installation and maintenance tips for solar-assisted heat pumps
When installing a solar-assisted heat pump, it is important to:
- Hire a qualified installer
- Read the instruction manual
- Follow the manufacturer's recommendations
- Check local building codes
- Get a permit from the local authorities
- Inspect the site before installation
- Prepare the installation area
- Install the solar collector
- Install the heat pump
- Fill the system with fluids
- Pressurize the system
- Test the system
- Install a thermostat
- Install an expansion tank
- Install a circulation pump
- Install a safety valve
- Install a check valve
- Install an isolation valve
- Install a drain valve
- Install a pressure relief valve
After the system is installed, it is important to:
- Read the instruction manual
- Follow the manufacturer's recommendations
- Check the system regularly
- Test the system regularly
- Maintain the system according to the manufacturer's recommendations
- Hire a qualified technician to service the system when needed
- Keep spare parts on hand
- Keep the system clean
- Protect the system from freezing
- Repair any leaks promptly
