What are solar heat pumps, the best system for heating and domestic hot water

The heating and the various systems to heat the water of our houses, represent a large part of the energy that our houses consume, the bills increase! But you can compensate for them, there are many efficient heating systems, such as solar-assisted heat pumps (SAHP), which some manufacturers claim can pay for themselves in two or three years of use.

These systems combine technology similar to solar hot water and air-source heat pumps to heat water or small spaces in the home.

SAHPs have been around since the 1970s, but their time may have come thanks to their high energy efficiency.


How does a solar-assisted heat pump work?

HPSA use solar thermal energy and heat pumps to produce heat. Although these systems can be configured in different ways, they always include five main components: collectors, an evaporator, a compressor, a thermostatic expansion valve and a heat exchange tank.


Surely you know what photovoltaic solar panels are, which convert the sun’s energy into electricity, but have you ever heard of solar thermal collectors or panels? Instead of generating electricity, the collectors convert sunlight into heat through their absorber plates. The heat generated is transferred to the refrigerant, a substance that absorbs and transports heat throughout the system.

There are several types of sensors you can use to maximize the efficiency of your SAHP, depending on the surrounding environmental conditions:

  • flat solar collector. Flat plate headers contain large, flat absorber plates that transfer heat to the coolant inside the header. They work most efficiently when the sun is directly overhead, so they are best suited for very sunny areas.
  • Empty tubes. The evacuated tubes comprise rows of parallel transparent glass tubes which are connected to a heating tube which contains the coolant. They work more efficiently than dinner plates, but they can also be prone to overheating and cracking at high temperatures, making them more difficult to maintain in hot climates.
  • PV-T or hybrids. PV-T or hybrid collectors combine PV solar cells and thermal panels. The excess heat produced by the photovoltaic cells is transferred through the thermal panel to the cooler. They significantly improve the efficiency and performance of SAHPs, especially since the electricity from the PV can be used to power the compressor. They don’t tend to overheat and can work well in both hot and cold climates.
  • thermodynamics. The collectors solar panel thermodynamics they use heat from the ambient air and the sun to heat the refrigerant as it passes through the panel. They do not depend solely on exposure to the sun and work at night and in winter. Thermodynamic collectors can be installed both on the sides of buildings and on roofs.


After the manifolds heat the refrigerant, the fluid evaporates into gas.

In direct expansion SAHPs, the refrigerant flows directly through the solar collectors and the absorber acts as an evaporator.

In indirect expansion SAHPs, the refrigerant is part of a closed loop system in which it passes from the collector to a heat exchanger which acts as an evaporator.

Thermostatic expansion valve.

The thermostatic expansion valve increases the efficiency of the SAHP by regulating the rate at which the refrigerant flows to the evaporator to increase energy production.


The gaseous refrigerant passes through a compressor which pressurizes it and concentrates the heat. The compressor needs electricity to operate, which can come from fossil fuels or renewable energy sources such as photovoltaic solar panels.

Storage tanks.

The pressurized refrigerant passes through a series of tubes called heat exchangers or condensers. The refrigerant condenses into a liquid and the system transfers the heat produced through the pipes to the water in its storage tank. Now the water is hot and you can take a hot shower.

How to compare different solar heat pumps.

The performance of your solar heat pump varies depending on its configuration and your place of residence. Before installing a system, you must answer the following questions:

  • Will I use the solar heat pump for water heating, space heating or both?
  • What type of climate do I live in and what system will work best for that climate?
  • What type of energy will I use to power the compressor?
  • Do I already have some of the components that I want to integrate into my solar heat pump?

How to assess the efficiency of solar-assisted heat pumps.

Before choosing a solar heat pump, you should compare the coefficient of performance (COP) of different systems.

The COP is a measure of the efficiency of the heat pump which is based on the ratio between the useful heat produced and the energy supplied.

A higher COP equals a more efficient heat pump and lower running costs. Although the highest COP a heat pump can achieve is 4.5, heat pumps with a COP above 3.0 are considered highly efficient.

Power your compressor with photovoltaic solar panels.

To maximize your monthly savings, you can install solar photovoltaic panels in addition to your SAHP to supply your compressor with free, clean electricity.

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