When it comes to choosing renewables technologies, where do you start?

For some, the need to limit our current energy usage is rooted in concerns around global warming and mitigating the effects of climate change.  For others, it’s more about peak oil, rising energy prices and fuel poverty.   Whichever side of the fence you sit on, the outcome is the same – our dependency on fossil fuels is unsustainable.

It is estimated that, globally, building stock consumes approximately 40% of our annual energy requirements and is responsible for a similar percentage of our CO2 emissions. So, not surprisingly, the UK government and the construction industry are taking decisive action to lower this demand.

The starting point, of course, is energy efficiency. Having a properly sealed building envelope, with energy efficient appliances, lighting etc, is rightly regarded as the first step for home owner and office block contractors alike. The next step is to generate more energy in-situ through renewable technology (now a requirement to meet Part L of the Building Regulations).

Which technology?

Deciding which technology to install which will deliver against the aims and objectives of the project requires careful consideration. The process usually starts with a review of both the building’s budget and a calculation of the potential CO2 savings achieved with various solutions (solar panels, air source heat pumps etc) to determine which could be installed to achieve the required environmental standard. Once a viable technology has been identified, typically, the designs are passed on to the manufacturer’s engineering team to size and specify a system.

While the process may be fairly well-established, there are a number of variables that should be accounted for because of the impact they could have on the benefits provided by the technology in terms of both payback and its effectiveness.

Some renewable technologies, for example, are better suited than others for particular buildings, with suitability largely determined by factors such as the building’s occupancy, use, location and requirement for energy.

There are also other considerations that might mean the best solution on paper doesn’t work in practice; for example, the property’s size, style, or aspect might rule out the installation of one technology, but support another.

Getting it right first time can save a considerable amount of time and design cost but perhaps more importantly, the right solution means the system efficiency and payback time will be optimised.

Engineering expertise

Bringing in the expertise and experience of a manufacturer’s engineering team to advise on solutions before designs are finalised is highly recommended to help save a great deal of money, time and effort. That said there are also some general principles that are worth being aware of when reviewing options for renewable technologies.

For instance, solar thermal, which uses the sun’s energy to heat water, works particularly well for a building that has a heavy, constant requirement for hot water, such as a swimming pool, or a care home. Solar thermal works well in domestic settings too, where there is typically a steady demand for hot water (bearing in mind, that occupancy levels are more important than the size of the house when sizing a system).

Other buildings might have a high demand for hot water but the requirement may not be constant, such as in university halls of residence. Here, the engineers must carefully calculate the annual load profile when sizing a solar thermal system, understanding that occupancy levels will drop during the hot summer months, and as a consequence, so will hot water demand. If this is not factored in, not only will the solar thermal system be larger and more expensive than it needs to be, but because it will be oversized, it also runs the risk of over-heating.

For space heating and hot water, biomass boilers are commonly specified, not least because they are an easy switch from an oil boiler. However, the need for regular access to a building can mean that a biomass boiler is not the best solution. For example, deliveries of pellets by an articulated lorry may not be viable if a building is in a remote setting, and/or pellet storage may be problematic in some situations because of the size of the silo or hopper required.

Air source heat pumps

More recently, air source heat pumps – a relatively new technology – have become increasingly popular for space heating in both domestic and commercial applications. Not only can they extract heat from the air all year round, they are also extremely powerful with the technology developing further all the time. They typically have relatively low running costs and can reduce CO2 emissions by as much as 50%.

Air source heat pumps are particularly suited to under floor heating systems with relatively low flow and return temperatures and are very easy to install without any fuel storage requirements. However, they wouldn’t be suited to the production of high volumes of hot water for commercial applications where water temperatures may need to be in excess of 80°C. In these instances, solar thermal solutions would probably work better.

Small wind turbines, such as our KW3 and KW6, and shortly to be launched KW15 turbines, offer a year-round source of energy for some developments. Wind speed is particularly important in determining their potential effectiveness; usually a minimum of 5 metres/second is required, but the power output can be very impressive. A single KW6 turbine can produce yields ranging from 9,000kWh to 25,000+ kWh p.a., depending on wind speeds. This, along with the need for exposed sites to lower air turbulence, means they are particularly popular with the agricultural and rural communities. High wind speeds of course can be just as much of a problem, such that some wind turbines have to be shut down. It’s worth doing your research and choosing a turbine that offers continuous operation and power output regardless of wind speed.

Renewables technologies can also be combined to great effect. Armstrong Point, a business park in Wigan which is one of the few developments in the world to have achieved a BREEAM Outstanding rating, combines a wide range of renewables, including air source heat pumps, solar thermal and wind. They include a 6kW Kingspan Wind Turbine, seven Aeromax Plus 6kW air source heat pumps, seven Aerocyl 210 L Twin Coil Cylinders, and seven Thermomax HP400 2SQM solar thermal systems. As a result not only is the carbon footprint of the park vastly reduced, but for the first time in the UK, the park’s tenants will not pay a penny for the energy they use.

Whatever choice of technology is finally made, correctly sized, we calculate that our renewables technology could payback within six to seven years if sited, designed and sized to optimize efficiency.

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