TYPOLOGIES OF FACILITIES
A. PVT + Aerothermal System
All solar installations for DHW (Domestic Hot Water) production needs an auxiliary system (boiler, aerothermy, etc.) to heat the water up to its consumption temperature, especially on less sunny days. These auxiliary systems should be as efficient as possible so that they consume the minimum energy from the outside.
Aerothermal systems present a high efficiency ratio, as it only consumes 33% of the energy produced. These systems are perfectly combined with hybrid solar panels since firstly, the heat demanded by the aerothermal system is supplied by the hybrid panel’s heat production, and secondly, 50% of the electricity needed by the aerothermal system is supplied by the photovoltaic production of the hybrid solar panels.
As an example, in a domestic house, to cover the total amount of the DHW, 50% is saved with the hot water produced by the panels and the other 50%, is self-consumed by the photovoltaic generation itself (25%) and the other 25% is consumed from the network. Since the aerothermy usually has a COP of 3, the consumption of the network will be only 8% of the ACS consumed.
B. PVT + Geothermal System
Geothermal energy is another auxiliary installation tool that presents a high efficiency to heat the Domestic Hot Water. This system finishes heating the water from the temperature achieved by the panels to the consumption temperature. Of all the technologies based on the heat pump, geothermal energy is one of the most efficient. Thanks to this, the electricity consumed by this system is lower and, as a consequence, also its CO2 emissions are lower.
The high efficiency (high COP) of geothermal energy is due to the fact that the temperature of its cold focus (the soil) is stable and in the winter months it remains warmer than the environment. The colder the climate, the more advantage is obtained from geothermal energy compared to aerothermal systems. The opposite occurs in temperate and warm climates.
Combining geothermal energy with hybrid solar panels drastically reduces the energy consumption of a building. As an example, to cover the demand of DHW, the panels cover with their thermal production around 50%, and the geothermal covers the rest. To contribute the rest, geothermal self-consumes part of the photovoltaic production and the rest comes from the network (around 4% of total demand).
C. PVT + Biomass
Currently, one of the auxiliary systems with less environmental impact are biomass systems. In recent years, they have had an important development due to their implantation in buildings. These auxiliary systems should be as efficient as possible or emit the minimum amount of greenhouse gases (GHG) as CO2.
Biomass is a technology that uses forest residues and the CO2 emissions it generates for water heating is equivalent to its degradation in forests. Therefore, although biomass emits CO2, it is considered neutral, because it would do it in the same way in its natural degradation.
Hybrid solar panels combine very well with biomass, since, on the one hand, collectors contribute around 50% of the Domestic Hot Water demand and on the other hand, biomass only consumes fuel. That is, it does not consume electricity, so all the generated photovoltaic energy can be used in the building.
D. PVT + DHW and Swimming pools
Solar hybrid collectors are very suitable to be used in buildings with swimming pool. In summer, when there is more irradiation, and consequently the panels generate more energy (photovoltaic and thermal), besides producing DHW (Domestic Hot Water), also warms the swimming pool.
Using PVT panels with swimming pools, the hydraulic circuit work at lower temperatures getting a higher efficiency both photovoltaic and thermal.
Outdoor swimming pools cannot be warmed by an auxiliary heater (boiler, heat pump, etc) that consume fossil fuels or electricity (not renewable). Indoor swimming pools have to be warmed at least a 50% with renewable energy like solar hybrid panels.
E. PVT + DHW, Heating & Swimming pools
Most solar thermal installations in buildings usually only generate energy to be used in DHW. The technology is only applied for DHW and not heating because in summer there is no heating demand and also because in winter is when there is lower irradiation.
In those solar installations used to supply energy to the heating system it is necessary to predict the use of the surplus energy in summer. There are several uses like swimming pools. Using solar Energy in swimming pools allows recovering surplus solar energy in summer, lengthening the bathing session, and making bigger installations which achieve very important savings.
Also, combining PVT panels with swimming pools allows the installation to work at low temperatures increasing the thermal and photovoltaic efficiencies, achieving higher energy and emissions savings.
F. PVT + Adsorption (Solar Trigeneration)
Solar cooling consists in using the surplus thermal energy to activate an adsorption machine (or absorption) to cooling. Combining these machines with hybrid technology solar trigeneration is obtained since electricity, heat and cold are produced.
Our buildings demand 40% of the total energy in our countries. From all this energy demand, 20% is consumed by the Sanitary Hot Water (DHW) and the rest (80%) by the heating system. Saving 50% of the DHW demand with solar energy, only 10% of the total thermal energy demand of the building is saved. Consequently, it is necessary to apply solutions which can save more energy. All these installations need to solve the use of the
thermal energy surplus in summer.
Solar Trigeneration allows larger installations increasing the thermal savings from 10% (in average in DHW) to 80-90% depending on the building demands. In summer, this type of installation uses the thermal energy to activate an adsorption machine to cool the building. Thus, this technology will be use in all those buildings where high percentage of the energy demand want to be supplied by renewable energy. This innovative technology only will only be used in a select market due to its high cost.
G. PVT + Seasonal Storage
The main limitation of the solar thermal installations appears as the consequence that the higher generation (summer) occurs when the lower demand exists (DHW). For this reason, the solar energy only contributes around 50% of the DHW demand, which is around 10-20% of the total thermal energy demand of a building.
A reliable solution already used in some countries in north Europe is seasonal thermal storage. This technology stores the surplus energy generated by the panels during the summer to be used in winter. In this technology, on average, only 10% is lost. Consequently, 90% of the total thermal energy generated can be used 6 months after. The seasonal temperature variations in the storage tank is between 20ºC to 50ºC during the year. This thermal energy is used by the heat pump to supply the building energy demand. The higher temperature in the seasonal storage tank, the higher COP (Coefficient of performance) will be obtained. Also, a part of the total electricity consumed by the heat pump is supplied by the hybrid panels reducing the grid energy dependence.