Combined Heat and Power and Trigeneration

Renewable technologies will play an increasing part in our daily lives and DDAI has amassed a wealth of knowledge and experience in this area to apply to your projects.

Combined Heat and Power (CHP) generates heat and power in a single process and is markedly more efficient than conventional generation.

As such, it offers huge potential in reducing our energy needs. The logic is simple: the more efficiently the UK uses its fuel, the less reliant it needs to be on importing energy, the less it needs to spend and the less greenhouse gas that is emitted.

CHP has many applications from a relatively small system to providing the power and heat to a large complex such as a swimming pool or hospital. As the name suggests, CHP produces electricity, usually by burning gas as the raw material but with the potential for renewable fuels too, which drives an alternator. The bonus is that the heat used in the process is not lost up a chimney or cooling tower but recovered to provide hot water for space heating.

Precisely because CHP systems are usually located on the site where the energy is used, their overall efficiency levels are over 70% at the point of use. That is almost twice as efficient as power coming from conventional coal and gas fired power stations.

Official data puts the typical efficiency of these at just 38% and 48% respectively. And that is before factoring in losses that take during transmission and distribution when the power leaves the generating plant, so the actual efficiency figure falls even further.

Trigeneration

Trigeneration takes CHP to another level. In addition to using the waste heat to provide hot water and space heating, this power can be used to chill water for air conditioning during the summer months. The key ingredient is the inclusion of an absorption chiller. This allows water to be used as a refrigerant because it vaporises at a much lower temperature than conventionally.

DDAI has designed and installed many CHP systems of differing size and application, including trigeneration, and would be pleased to discuss your specific project requirements.

Biomass

Since the dawn of time, man has burned natural fuels such as trees to provide heat and light. Biomass energy production puts this oldest of practices into a 21st Century context.

As a fuel source, the use of biomass is growing rapidly and the UK can now boast its own production facilities for compressed wood pellets, which make use of waste sawdust to power boilers, though its development in this country still lags some way behind parts of Europe and North America.

The striking point is that as long as there is proper management of the process, biomass is not only sustainable but carbon neutral too. Although it does emit carbon dioxide (CO2) when it is burned, it will have absorbed a similar amount of CO2 from the atmosphere while it was growing.

Biomass is a long-term solution that falls firmly in line with the Think Global, Act Local slogans of environmentalists. Ideally it is used as close as possible to where it is grown to minimise the use of fuel in transporting the finished product to where it is needed.

Crops such as willow and poplar, together with others as diverse as elephant grass, reed canary grass and oilseed rape, are also used for biomass production after they have undergone extensive periods of drying to leave as little water as possible still within them. Because of the lack of moisture in the finished product, the fuel generally gives off little in the way of smoke particulates or sulphur dioxide, which is a key cause of acid rain.

There is also relatively little ash. Moreover, what ash is produced has the added advantage of being excellent for use as a fertiliser.

Plants and trees grown for fuel need replanting to make a virtuous cycle that keeps carbon emissions down and makes it truly renewable.

As an added bonus, financial help is currently on offer from the government for organisations seeking to generate renewable heat and using local resources that would otherwise go to waste.

DDAI can provide the full design and installation of biomass-only or dual fuel boiler plant/CHP to provide the full heating and domestic hot water requirements of your development.

Photovoltaic cells

Photovoltaic (PV) cells use light to generate electricity and PV panel technologies, include polycrystalline, monocrystalline and thin-film. Solar PV cells can be arranged in panels on a building’s roof or walls and can often feed electricity directly into the building.

With the latest PV technology, cells can be integrated into the roof tiles themselves. Groups of solar PV cells can be added together to provide increasing levels of power. This can range from small, kilowatt-sized solar panels for domestic households, to larger arrays, which function as separate solar power plants feeding power directly into the electricity grid.

PV panels are particularly suitable where a grid connection is difficult. The popular combination of a micro-wind turbine and PV panel uses the fact that there is more wind in the winter when the sun is weak and vice versa to provide a more reliable energy supply.

Due to their relatively high capital cost, the application of PV cells needs to be carefully considered. However, we can advise on the potential suitability for your project.

Rainwater Harvesting

At its simplest rainwater harvesting is the process of collecting rain which falls onto the roofs of buildings and then reusing it. Its most common application is for use in toilet flushing, which does not require tap-quality water.

Because rainwater falls naturally, it saves occupiers money by cutting their water usage. It also helps to cut the risk of flooding because water collected and stored does not enter the storm water drain system.

For housing developers, installing rainwater harvesting gives additional points towards the UK Eco-homes rating, while rainwater used for garden irrigation is better for plants and lawns because it has a balanced PH and contains no chemicals such as chlorine.

The complexity of the systems depends on their use; in domestic applications, it might be a case of just connecting a water butt to a downpipe for filling watering cans or using a cheap siphon system for a hosepipe.

In larger developments such as commercial offices, hotels and other buildings, more sophisticated measures will typically include pumps that either feed into a header tank or straight from the collection reservoir. Using rainwater harvesting does not expose occupiers to the vagaries of the weather because they can easily revert to the conventional supply if rainwater is not available.

BREEAM

BREEAM is the Buildings Research Establishment’s Environmental Assessment Method and it assesses the environmental impact of buildings in the UK. Buildings that successfully undergo this process receive ratings at Pass, Good, Very Good, Excellent or Outstanding.

A number of factors are used to determine this rating, not all of them technological. A building that has excellent environmental credentials but sits in a remote location without access to public transport for employees may find itself marked down as a result.

BREEAM sets the standard for best practice in sustainable design. For occupiers and developers, the objective nature of the accreditation process gives them a way of proving the environmental credentials of their buildings.

The process also inspires participants to seek out the optimal solutions to protect the environment and has become an unofficial benchmark for building performance.

DDAI has a wealth of experience in delivering buildings with a range of BREEAM score ratings - including Excellent - and can assist in the design and construction process to deliver clients’ aspirations.