While all organisations have an imperative to reduce their carbon emissions, the education sector is under particular pressure because of the government’s commitment to make all schools carbon-neutral by 2016. As a result, there is considerable emphasis in both the Building Schools for the Future (BSF) and the Primary Capital Programme (PCP) to include renewable energy sources in building designs.

In many cases, making the most effective use of the options available requires a combination of suitable technologies, often with biomass boilers at the heart of the scheme. Nottinghamshire County Council, for example, is about to install its 50th Hoval biomass boiler in a school. On occasions, biomass boilers are supplemented by other sources – perhaps by solar thermal heating and heat pumps. Some schemes also include ultra-efficient condensing boilers as well.

Clearly, this presents an inherent engineering challenge; insofar as many low or zero carbon (LZC) energy sources are variable in nature. So it’s important to select the right combination and make the whole system work efficiently. Hoval’s unrivalled expertise in integrating a range of low energy technologies has proved invaluable in guiding schools and other facilities to the optimum system design – and making the theory work in practice.

In many cases, a biomass boiler using wood as a fuel is at the heart of such a system and this may be combined with solar heating and/or heat pumps as well high efficiency conventional boilers. At York High School, for example, five Hoval STU biomass boilers (total heating capacity 2250kW) have been combined with 80kW of Hoval’s SolKit solar thermal heating systems. The latter, believed to the largest solar thermal array installed in the country so far, will heat the swimming pool for most of the year with back up from the boilers when necessary. Hoval worked closely with York City Council to deliver a comprehensive package.

“One of the reasons we’ve teamed up with Hoval is their willingness to provide a complete package from initial site inspection right through to ongoing maintenance,” explained the Council’s Sustainability Engineer George Sands.

“So as well as supplying the boilers, fuel storage silos and fuel transfer system, they organise siting of boilers in plant rooms, connection and commissioning. This gives us one point of contact and total clarity of liability and risk.

“The products are also backed by a support package tailored to our needs, so we can be assured of a swift response in the event of problems. The fact that the boilers are manufactured in the UK also means there is lower embedded energy in each project,” he added.

Local manufacture was also a key consideration in the choice of a Hoval BioLyt biomass boiler for a new building at Bowbridge Road Primary School in Newark. Here, biomass technology is again combined with solar heating, along with a range of other environmentally friendly design features introduced by Nottinghamshire County Council to make the building as close to carbonneutral as possible.

Just as importantly, the boiler is designed to minimise input from the school’s maintenance staff, an important consideration for any school where such resources are limited – and especially so in primary schools where support staff are often shared between schools. Consequently, incorporation of features such as self-cleaning, automatic fuel feed and automatic ash removal in the boiler all help to keep maintenance costs down.

At both of these schools, the choice of biomass fuel has been wood pellets. “Using carbon-neutral biomass fuels is a very quick way to reduce carbon emissions, especially in older buildings where heating may account for as much as 40% of emissions,” George Sands noted. “However, before proceeding with any such project it’s vital to establish which type of technology will deliver the best results. After a lot of research we concluded that wood pellets derived from wood processing waste offered the best results when biomass is the selected technology,” he added.

The factors that contributed to this choice included criteria such as combustion efficiency, storage and delivery requirements. In more rural locations, locally produced wood chips may be a more suitable option and Hoval has recently launched its Forester boiler to address these situations.

Biomass can also prove to be a highly cost-effective alternative when replacing old coal-fired boilers. As part of its overall commitment to reducing carbon emissions, Caerphilly Council has replaced four old coal-fired boilers at Pontllanfraith secondary school with three 350kW STU wood-burning boilers from Hoval.

As well as new boilers, mechanical contractors Lorne Stewart also installed new stokers and feeders, enabling the pellets to be fed automatically to the boilers to provide precise control of heat output. The boilers are linked to a control system which brings them on in sequence as and when required.

The wood pellets are derived from sustainable sources and the carbon dioxide they produce during combustion is equivalent to that consumed by the trees during growth, making them carbon-neutral. A further benefit to the council is an increase in energy efficiency.

“Although wood has a slightly lower calorific value than coal, the new Hoval boilers are 90% efficient, compared to the 68% efficiency of the coal-fired boilers, so we are achieving significant improvements in efficiency,” commented John Davies of the council’s Property Service’s department. “The boilers have now been operational for around six months and we are very happy with their performance,” he added.

Staying in control

As noted earlier, the key to any such projects is to make sure all of the systems that contribute to heating and hot water work together in harmony. For example, when there is plenty of solar energy available it makes sense to use it to its full potential. When there is less, it can be used to pre-heat hot water, with other sources kicking in to bring the water up to temperature.

As a company that manufactures biomass boilers, solar heating systems and heat pumps – as well as ultra-efficient gas and oil fired boilers, Hoval has vast experience of providing integrated, optimised systems that give maximum performance throughout the year. This results from a combination of engineering expertise and a profound understanding of each technology, backed by advanced controls systems that we have developed to address these challenges.

In addition, we are able to offer comprehensive packages that go far beyond the supply of equipment to encompass every stage of the project from initial design right through to final commissioning and ongoing maintenance. We also have considerable experience of working with local authorities and individual schools to ensure that individual requirements are fully addressed.

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