The importance of thermal storage
Because many forms of renewable and recovered energy are not necessarily available when they are most required, thermal storage has a vital role to play in realising building-services systems that are both energy and cost efficient. This thermal store from Capito can accept energy from a variety of sources.
David Whitfield explores the central role that multi-energy thermal storage has to play in the design and delivery of an energy and cost efficient building system.Energy costs are increasing daily at an alarming rate, and due to speculative, political and economic factors look destined to continue on this upward spiral. Equally, we all know that to sustain our planet we must reduce carbon-dioxide emissions, the major contributor to global warming. In this economic and environmental climate, two requirements that are top of the priority list when designing any building system are making it energy efficient and making it cost efficient. As these two topics have become increasingly top of the agenda over recent years, the industry has responded accordingly, and there has been a welcome change in attitude to a focus on energy conservation and the use of renewable energies — both for the sake of the bottom line by containing energy costs and the environment by improving energy efficiency. Careful analysis shows, however, that unfortunately these changes have brought only some of the expected benefits. In fact there is growing awareness that we can only partly replace high-cost energy. Solutions need to be found that integrate a variety of energy sources — creating the right energy mix to provide comfort and optimum performance, whilst minimising harm to the environment, energy costs and ongoing management costs. Evinox is currently applying such solutions to a variety of projects. The nature of the projects is diverse — including a luxury house with seven bedrooms and six bathrooms, a communal heating system and a rhino enclosure at a zoo. However the central component in all of these projects is the same — Capito’s award-winning multi-energy thermal store For a luxury home in north London, Evinox provided 9 m2 of evacuated solar tubes, a 1250 litre thermal store to generate heating and hot water and alongside a Geminox condensing boiler for top-up energy. Atlanta Boulevard in Romford has its 98 apartments served by a communal heating and hot water system. Evinox supplied 110 m2 of evacuated solar tubes, which feed two 1750 litre thermal stores. The energy in the stores in turn feeds the communal system, with Evinox Modusat satellite heating units in each apartment. The solar controller registers the energy supplied from the solar tubes and signals the boiler plant to come in to help when required. The system was designed to meet a 10% renewable contribution. The rhino enclosure at Whipsnade Zoo is having its hot water for the rhino showers, the heating of the rhino pool and the heating of the air handling unit for the enclosure all generated by evacuated-tube solar energy. The 1500 litre thermal store allows the solar to combine with an air-source heat pump to top up any energy requirements not met by solar energy in the winter. When Evinox researched the best use of renewable technology with partners across the EU, the key ingredient was harnessing the energy when it was available and storing it ready for times of demand and not wasting it when it was available by not being able to store it. We have found the multi-energy thermal store to be the best solution when using several energy sources — solar, biomass, gas, heat pump etc. If an energy-integration process is to be efficient, the various elements involved must be managed by a single unit, which is capable of controlling the operation as a coherent whole and always gives priority to renewable sources.
Atlanta Boulevard in Romford has two 1750 litre thermal stores to maximise the use of solar energy from 110 m2 of evacuated solar tubes.
The heat-transfer system in the Capito thermal store uses gravity rather than more common circulating pumps or control systems, which both need energy and maintenance, incurring additional costs. This heat-transfer process also enables the hot water to be brought from the bottom to the top of the store, where it can be used immediately without waiting for the remaining buffer water to be heated up. The stores are sized from 250 litres up to 3000 litres and 5000 litre units to order. Such thermal stores can also recover and re-use the heat from several different processing operations or services (e.g. heat from condensation in everyday refrigeration units, which is usually dispersed into the atmosphere, or heat from fluid cooling processes etc.). When designing an energy-efficient, yet also cost-efficient, building system it is clear that the solution offered needs to integrate a variety of energy sources. The thermal store is the key component in the solution, as it can be adapted to fit any number of energy sources, prioritise the renewable sources, minimise the use of high-cost energy sources and maximise energy efficiency — whilst never compromising on quality of heating and hot water delivery. In the tricky balancing act between financial and environmental concerns, the thermal store provides the answer — minimising both financial and environmental costs. David Whitfield is managing director of Evinox Ltd.