What are Thermodynamic Solar Panels?
Thermodynamic solar panels extract heat from both daylight and the ambient environment to give you hot water. Their main advantage is better efficiency than an immersion heater. This makes them cheaper to run. However, thermodynamic solar panels compare badly to some other alternatives. In particular, they only provide hot water for your shower and taps, not for space heating. Don’t buy thermodynamic solar panels before you read this article!
How do Thermodynamic Solar Panels Work?
Thermodynamic solar panels work on the same principal as a fridge: Pumping heat from one place to another. The difference is that instead of cooling down your food they heat up your water. This makes them a kind of hybrid between a solar thermal panel and a heat pump. If you like, see the green box for more details. Feel free to skip the technical explanation if that’s not for you 🙂 From the user’s point of view, thermodynamic solar panels do basically the same thing as an immersion heater – but use less electricity.
Technical Explanation: First, fluid passes through an expansion valve and becomes very cold. To make it less cold, it then flows into the thermodynamic solar panel. Once inside the panel, the fluid sucks up any warmth it can find. It will suck warmth out of sunlight, rain, and even the ambient air. Next, the fluid goes into a compressor. Compressing the fluid makes it hot. This compression and heating is the key step. Once the fluid is hot, it flows through a coil inside your hot water cylinder. From here, the heat goes into the contents of your thank, giving you hot water. The process is now complete and the fluid goes through the expansion valve again to continue the cycle.
- More efficient than immersion heaters
- Overheating is not a problem
- Light weight makes installation easy
- Durable in outdoor environments
- Takes up relatively little roof space
- Does not lose efficiency over time
- Antifreeze not required
- Can work at temperatures well below zero
- Can work without sun and even at night
- Uses much more electricity than solar thermal panels
- Not optimised to take advantage of cheaper night-rate electricity
- Less efficient than air-source and ground-source heat pumps
- Don’t provide hot water for space heating
Cost to Run Thermodynamic Solar Panels Versus Immersion Heaters
In 2014, a company called Narec tested the efficiency of a thermodynamic solar panel system. They found that the coefficient of performance for the system was between about 1.5 and 2.2. This means that the system used approximately 33-55% less electricity than a typical immersion heater would have. In euro terms, that’s about €250 – €450 per annum for a family of five. So thermodynamic solar panels beat immersion heaters in terms of efficiency and running costs.
Cost to Run Thermodynamic Solar Panels Versus Heat Pumps
Thermodynamic solar panels look a lot less favourable when you compare them to heat pumps. First of all, heat pumps tend to have a better coefficient of performance (~2 – 3.5) than thermodynamic solar panels (~1.5 – 2.2). Secondly, many heat pumps provide not only hot water to your taps, but also hot water for space heating. Overall, a heat pump saves more energy than a thermodynamic solar panel.
Solar Panel + Heat Pump 2-in-1
In theory, thermodynamic solar panels combine the advantages of both solar thermal and heat pumps in one device. However, the reality is more of a “worst of both worlds” result. One the one hand, thermodynamic solar panels lack the insulating glass covers of solar thermal panels. For this reason, the fluid in the panels struggles to reach the high temperatures that solar thermal can achieve. On the other hand, thermodynamic solar panels lack the high-power fan of an air-source heat pump. This hinders their performance whenever the sun isn’t out.
Are They Eco-Friendly?
Thermodynamic solar panels use less electricity than immersion heaters. This is a clear positive for the environment. However, heat pumps are a better choice because they use even less electricity. Best of all are solar thermal panels which use only a tiny amount of electricity for the pump. Overall, thermodynamic solar panels compare well to immersion heaters but poorly to other options in terms of energy consumption.
Another consideration is the fluid inside the panels. Both thermodynamic solar panels and heat pumps depend on refrigerants to make them work. Often, these refrigerants contain HFCs. This is an issue because HFCs are extremely potent greenhouse gases. Any leaks pose a serious environmental risk. On the other hand, immersion heaters and solar thermal panels don’t contain refrigerants. If you’re concerned about the environmental impact of HFCs then look for heat pumps and thermodynamic solar panels with supercritical CO2 or hydrocarbon refrigerants, instead of HFCs.
Thermodynamic solar panels provide hot water by pumping heat from the environment into your hot water cylinder. This makes them more efficient than immersion heaters. However, they are less efficient than ground-source and air-source heat pumps.
PV Solar Panels For Hot Water
Immersion heaters; thermodynamic solar panels; heat pumps. They all have one thing in common: Electricity. No matter which option you choose, you can save money by powering it with electricity from PV solar panels. Better still, you can use a clever device called a solar panel power diverter to heat water using PV solar panels. For most people, this is the most cost-effective, rewarding, and reliable way to heat water with solar panels. Read Are Solar Panels Worth it in Ireland? or enter your Eircode below to compare quotes from Ireland’s best solar installers: