Renewable energy in buildings

Saving energy through increasing energy efficiency in buildings is of prime importance globally. The two main pillars of this are reducing the energy consumption of buildings and integrating clean, renewable energy sources into the built environment.Renewable energy in commercial buildings

Fortunately, we have access to various renewable technologies that can provide much, if not all, of the energy needs of individual buildings and small communities. These technologies include solar photovoltaic (PV)s, wind turbine systems and hydroelectricity. Also, micro-CHP systems, while not in themselves necessarily renewable, can provide significant improvements in efficiency and can form part of the overall green energy solution.

Solar PV

Currently, solar PV is the single most important renewable energy technology for buildings. Solar energy is available worldwide, once installed the systems produce zero greenhouse gas during operation, they are silent, and they don’t rely entirely on bright sunny days. PVs also work the skies are cloudy, though not as well as when the sun shines brightly; they will still generate 10% to 25% of their output.

PVs can be installed on rooftops, over car parks, and can be incorporated into architectural features. In many cases just covering half of the available rooftop space which can theoretically provide all the energy the building requires.

Although the Feed-in Tariff schemes have closed to new applicants, you can still apply for the Smart Export Guarantee, which will compensate for the power you return to the grid through solar PV panels.

Wind turbines

Wind turbines are providing ever-increasing quantities of green electricity. While most is produced through windfarms, micro-wind turbines are making a significant contribution to local electricity generation. Micro wind turbines may be mounted on or close to individual buildings, and there is a growing number of larger buildings that have incorporated wind turbines into the architecture.

Building-mounted turbines must overcome several problems. Turbines work better with laminar air flows, but in built environments, air flows tend to be turbulent and unpredictable. However, the latest generation of integrated wind turbines uses lightweight materials for the turbine blades and new rare-earth magnet generators which, along with improved aerodynamics, makes them sensitive to low wind speeds. They can generate electricity at wind speeds of just a few metres per second.

The problem of noise has also been addressed using low noise blade design, vibration isolators, and sound dampening materials. They are also designed to be more attractive architecturally.

They also qualify for the Smart Export Guarantee for the power they return to the grid.

Hydroelectricity

Wherever water falls or flows, there is the potential to generate hydroelectricity. It can be generated by streams, rivers, lakes, reservoirs and dams. As a green technology, it is very appealing, and the necessary technology is firmly established. Power conversion efficiencies can be higher than 90%. In the UK, about 14% of renewable electricity generation is hydroelectric, mainly from large and medium scale hydro plants.

However, many micro-hydro schemes have been installed that provide enough power for several houses and even small communities. While such installations have high capital costs, they require little maintenance and can generate electricity 24 hours a day, offering a considerable advantage over solar and wind. Micro-hydro systems do not damage the environment and can be engineered to last for 50 years.

As with solar and hydro, they qualify for the Smart Export Guarantee

Micro CHP

Micro combined heat and power technologies simultaneously produce heat and electricity from the same source. Usually, micro-CHP solutions provide mainly heat. Typically, the heat/electricity ratio is around 6/1.

Micro-CHP is usually gas powered, though bio-fuel powered systems are in development. While most systems still consume fossil fuels, they are more efficient than separately sourcing electricity from the grid and burning fossil fuels for heat.

Domestic micro-CHP systems are similar to conventional domestic gas-powered boilers, though with additional technology, such as a Stirling engine generator or fuel cell, for producing electricity. Electricity generation is powered by heat from exhaust gasses which would otherwise be wasted. Efficiencies are exceptionally high; systems are available with up to 92% efficiency.