Solar-powered heating and cooling system developed

Solar panel systems that both heat and cool buildings may soon be coming to a large office building near you, thanks to engineers at two Spanish universities.

Engineers from Madrid’s Carlos III (UC3M) and Politécnica (UPM) universities have developed a model that involves the incorporation of solar collectors into a gas-based cogeneration system with an absorption machine, which would reduce both energy expenditure and CO₂ emissions.

The model makes the best possible use of trigeneration systems in order to allow maximum reductions in energy expenditure and CO₂ emissions. Furthermore, the model’s ability to accommodate solar collectors is a feature new to the field, the engineers say.

“Current regulations state that the installation of solar panels in buildings is only compulsory in order to meet the demand for domestic hot water, but very few offices have either showers or kitchens,” said Pedro A Rodriguez, UC3M professor and primary author of the study.

“Consequently, the idea behind our proposal is that a part of the demand for heating in winter and for air conditioning in summer be met with solar power.”

In order to create the model, the team considered the energy needs of the buildings within the Madrid region, as well as monthly climatological data - temperatures and solar radiation - pertaining to the area. The system makes it possible to provide air conditioning or heating according to the specific daily needs of each office, which may vary - particularly in spring and autumn.

The researchers apply a ‘coefficient of merit’ as a decision-making tool in order to save energy and to operate the hybrid trigeneration plant. This plant supplies 1.7 MW of electricity, 1.3 MW of heating and 2 MW of air conditioning. It can be installed in a business park of 50,000 m², in which offices are linked together with two rings, each a kilometre in length. These rings follow the path of the sewage works or other underground pipes.

“The size of the investment necessary for the installation of a solar power plant means this hybrid solution takes longer - more than 14 years - to pay for itself,” said Carmen Rodriguez Hidalgo, UPM researcher and co-author of the study.

“However, the system allows greater reductions in CO₂ emissions, ranging from 1527 to 1760 tonnes per year. It also produces primary energy savings and a slight increase in annual profits.”

Details of the system appear in the journal Applied Thermal Engineering.