Public administration bodies may manage a substantial number of properties with considerable needs for heating and power. The implementation of low-carbon technologies in these buildings can have an important beneficial impact on the environment. The supply of electricity in those buildings is generally provided by the national grid, which is outside the scope of action of the municipalities, but local public administration bodies are still able to promote renewable energy sources through on-site electricity production systems, thus reducing the overall impact in terms of carbon emissions.
Heating is generally generated on-site with a boiler running on gas or other fuels (biomass or solar thermal systems). Another option can be the implementation of a small-scale combined heat and power system (mini-CHP) still running on gas or biomass, where the better overall efficiency is due to the joint operation.
The first step to undertake before installing any on-site renewables and mini-CHP systems should always be the adoption of measures aimed at improving the energy efficiency of public buildings (12) and social housing (13) and those that improve performance through monitoring, energy management and fostering of behavioural change (15). Once the overall energy consumption of the facility is optimised by implementing these actions, it is possible to size the renewable energy systems and mini-CHP to the real energy demand of the building, thus optimising the installation and avoiding future operational and maintenance problems.
The most common renewable energy options for on-site electricity production in buildings and houses are solar photovoltaic panels, small-scale wind turbines and geothermal sources and biomass/biogas, while heat production from renewable sources is usually obtained with solar thermal panels or tubes and biomass/biogas.
Each option must be assessed based on the characteristics of the building and site, actual energy/heat needs, local climate, technical requirements, budget availability and so on.
If renewable electricity and heat cannot be generated for economic or technical reasons, or is insufficient to cover the building’s needs, other low-carbon energy options can be considered such as a mini-CHP or a heat pump.
As said before, a CHP involves the production of electricity and useful heat from a single plant, which is more efficient than generating electricity and heat separately. Mini-CHP refers to small-scale CHP systems that may power individual buildings or complexes such as hospitals, schools or social housing blocks. A CHP can be fuelled using fossil fuels, being a lower carbon system, or by renewable fuels such as biomass, where it is zero carbon.
In the case of heat pumps, the system uses electricity to drive a refrigeration cycle to extract heat from the environment (air, water, sea, ground). Although the heat is renewable, the pump still needs electricity or other fuel to drive the system.