Solar power generation system is a way to generate electricity using solar energy. Solar thermal system is to use solar energy to heat or produce hot water.
Comparison: Solar Thermal vs. Solar Electricity
When it comes to the question of “solar thermal vs. solar electric,” you have to decide which type of energy you want to generate. Solar thermal uses the sun’s energy and converts it into heat. The heat can be used for heating or hot water. On the other hand, solar systems use sunlight to generate electricity. Let’s take a closer look at the other differences.
Different Uses
Both solar thermal and solar systems are installed on the roof of the house and have their respective advantages and disadvantages. A solar system requires more roof space, while solar thermal collectors are more expensive. Your decision should be based on your individual requirements.
If you have sufficient roof space available, you can also consider a combination of both systems. Combined installation and use are possible without any problems.
Use of Solar Systems
Solar systems can be used to generate electrical energy that can either be used in your own household or sold. The electricity is sold by feeding it into the public grid. You receive a feed-in tariff for this from your grid provider. However, this has fallen sharply in recent years and the price of electricity has risen. Most owners of a PV system therefore opt for self-consumption of the electricity, as this is more economical and saves a lot on electricity costs in the long term.
You can use the electricity from your solar system not only for electrical appliances, but also for heating or to heat your domestic water. This is possible, for example, with an electric heating rod or in combination with a heat pump. This combination also increases your self-consumption, as you use more of your solar power yourself. An additional electricity storage unit even provides you with your own solar power at night.
Use of Solar Thermal Energy
With solar thermal energy, the heat from the sun is used to support the heating system or to heat domestic hot water. Solar thermal systems cannot produce heat for sale and are only intended for personal use. Solar thermal systems can provide a large proportion of the heat required for hot water preparation, but are usually not sufficient for the entire heating requirement.
However, this also depends on the type of building. New buildings generally have a lower heating requirement than old buildings. This is partly due to better thermal insulation and newer heating systems.
Different Modes of Operation
Both solar modules and solar thermal modules consist of several layers. In solar modules, solar cells are responsible for electricity production. Solar thermal collectors, on the other hand, consist of tubes that have a special fluid for heat transport.
Solar Function
Solars works by shining sunlight onto the PV cells. The light sets the electrons in motion and direct current is generated. The direct current is then converted into usable alternating current in the inverter. From there, the electricity runs to the electricity meter and finally to the domestic electricity grid or electricity storage system for consumption.
Solar Thermal Function
Solar thermal energy works using the infrared light spectrum of the sun. The tubes of the collectors absorb the radiation and heat a special liquid inside. The warm liquid is drained off and fed to a storage tank containing water. In the storage tank, the heat is transferred to the water and then pumped into the heating circuit.
Required Roof Area
The roof area required for solar thermal and solar systems differs greatly. Solar require considerably more solar modules as they are less efficient. Solar thermal systems, on the other hand, get by with just a few square meters. In addition, it is often worthwhile to cover the entire roof area with solar, as the costs fall in relation to the increasing number of PV modules.
This is How Much Roof Area is Required For Solar
With solar system, a roof area of around 50 m² is required to cover an annual electricity consumption of 4,000 kWh. This corresponds to the average consumption of a single-family home. On average, you can assume an output of 1 kWp per 5 m² area with solar modules. Added to this are the required clearance areas.
This is How Much Roof Area Solar Thermal Requires
In the case of solar thermal energy, the size of the roof area depends on the type and use of the collector. A flat-plate collector requires 4.5 to 7.5 m² to cover the hot water needs of 3 to 5 people. A tube collector requires only 4 to 6 m². For heating support, 7 to 11 m² are required for a flat-plate collector and 5 to 9 m² roof area for a tube collector.
Different Levels of Efficiency
At 60% - 90%, solar thermal systems have a higher efficiency than solar systems. The efficiency of the latter is 15 - 20%. Solar systems also have a more sophisticated technology, but they are easier to install as prefabricated modules are available. Solar thermal systems, on the other hand, require pipes to be laid and a boiler and pump to be installed.
Solar System Efficiency
The efficiency of solar systems is 10-25%, depending on the type of module. Monocrystalline solar modules have the highest efficiency of up to 25%. They are also the most expensive PV modules. Polycrystalline modules have an efficiency of around 16% and are slightly cheaper. The efficiency of thin-film modules is between 10 and 13%.
Solar Thermal Efficiency
The efficiency of solar thermal energy depends on the type of collector and the inclination to the sun. The efficiency of flat-plate collectors is between 60% and 85%. With tube collectors, an efficiency of 90% can even be achieved. Tube collectors are correspondingly more expensive.
Cost Comparison of Solar and Solar Thermal Energy
For single-family homes, the cost of solar system is between €5,000 and €15,000, depending on the size of the system. This includes assembly, installation and commissioning. The costs for solar thermal energy for hot water are around €5,000. For heating and hot water it is around €10,000.
Solar System Costs
A smaller 5 kWp system can cover the average annual consumption of a single-family home. The costs per kilowatt peak of solar output are between €1,000 and €1,800. A 5 kWp solar system therefore costs around €7,000. An additional electricity storage unit costs just under €5,000 extra. The costs can be reduced with subsidies.
Solar Thermal Costs
The costs for solar thermal energy depend on whether the system is only intended for hot water or whether heating is also to be supported. Costs of around €5,000 are incurred for the preparation of hot water in a detached house. For hot water and heating support, the costs are around €10,000.
Hybrid Modules: Combining Solar Thermal Energy and Solar
Solar thermal energy and Solar Generation can be easily combined. This is possible with two separate systems or with so-called hybrid modules (also known as PVT modules). A hybrid module consists of solar modules on top, which collect the sunlight, and solar collectors underneath, which absorb the heat. In this way, electricity and heat are produced simultaneously.
Hybrid modules are particularly suitable when a lot of heat is needed all year round, especially in summer. This is unlikely to be the case in a private household, as hot water consumption is limited and heat is usually only required in winter. Hybrid modules are therefore more suitable for facilities such as public swimming pools, hospitals or hotels.
For detached houses and apartment buildings, a combination of hybrid modules with additional solar modules is more likely to be worthwhile. However, the decisive factor is your individual need for electricity and heat.
Conclusion: Solar Thermal, Solar System?
| Solar System | Solar Thermal | |
|---|---|---|
| Technology | Solar modules | Solar collectors |
| Use | Electricity, hot water, heating | Hot water, heating |
| Feed-in Tariff | Yes | No |
| Subsidies | Yes | Yes |
| Required Area | Large | Small |
| Operating Costs | Very low | Relatively low |
| Payback Period | 10 - 20 years | 15 - 20 years |
| Lifespan | 25 - 40 years | 20 - 30 years |
| Initial Costs (Single-family house) | €5,000 - €15,000 | €5,000 for hot water, €10,000 for heating and hot water |
PV systems are particularly worthwhile for households with high electricity consumption. All that is required is a sufficiently large roof area. Due to rising electricity costs, the highest possible self-consumption of solar power is the most economical. To increase self-consumption, an additional heat pump or electricity storage unit can be installed. With the heat pump, you can reduce your heating costs as well as your electricity costs.
Solar thermal systems only require a small roof area. In existing buildings, solar thermal systems are generally only used to heat water, as the building envelope is often poorly insulated. In new buildings, solar thermal energy is also used to support the heating system.
One kilowatt hour of heat costs less than one kilowatt hour of electricity, which is why photovoltaics can often save a lot more money. Electricity is also much more versatile, as it can also be used for heating or for heating domestic hot water. Ultimately, however, it depends on your individual consumption and the conditions of the building.
