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Meeting the challenges of cost effective energy efficiency in buildings

IMAG0021-(1) The University of Ulster’s Centre for Sustainable Technologies has been at the forefront of developing cost effective new and renewable energy systems appropriate for domestic applications and especially when considering the retrofit market. Fears over rising domestic energy bills driven by a need to diversify energy supplies for strategic and environmental reasons may be partially offset by impending shale gas exploitation, but the fact remains that “fuel poverty” is increasing significantly and many existing energy efficiency and renewable energy solutions are not cost effective, even with a Green Deal style approach to long term financing and the sharing of savings.

The Centre for Sustainable Technologies has developed through its external funding from, for example, Science Foundation Ireland, Engineering and Physical Sciences Research Council, EU Framework Programmes, Invest Northern Ireland and University of Ulster Innovation Funds, a number of technologies that are promising in terms of challenging the fuel poverty agenda. These areas include solar water heaters, advanced glazing systems, heat pumps and energy storage and such areas are compatible with the broader energy context of greater integration of non-dispatchable renewable energy systems such as wind etc.

The SolaCatcher is a patented low cost passive solar water heater designed specifically for pre-heating domestic hot water. The system is a novel solar water heating design in both operation and installation in that the system can be installed on elevations as opposed to roofs. It has the potential to improve upon the cost-effectiveness of traditional forms of solar water heating technology.

The SolaCatcher is constructed from 3 concentric tubes. The outer tube forms the aperture and unit casing. It is made from a transparent material such as glass or Perspex. Its role is to protect the absorbing surface of the next vessel and reduce convective heat loss as well as defining the physical appearance of the unit. The remaining tubes (vessels) combine to create the collector/storage element and are arranged to create an annular space between the concentric walls of these inner and outer vessels.

The annular space is partially evacuated to a near vacuum condition and contains a small amount of water. During collection periods, solar radiation incident is on the outer absorbing surface of annulus chamber (coated with a selective film) and causes the water to boil at low temperature thus producing a vapour.

The water vapour condenses on contact with colder inner vessel surface and the collected thermal energy is transferred to water store through latent heat exchange. Condensed water runs down the vessel to a reservoir at base of annulus to continue the cycle. During non-collection periods no evaporation takes place due to the partial vacuum in the annulus chamber, thereby reducing heat loss from the store.

PRESOL-Full-Assy-2-Top-(1) The potential benefits of the SolaCatcher are:

• reduced pipework and fittings as can be mounted on elevations

• solves traditional issues of limited roof space / plant room

• passive operation, requiring no parasitic energy during operation

• inherent freeze protection

• lightweight unit

• suitable for retro-fit installation

• straight forward installation process requiring fewer trained artisans, less time and reduced resources

• low maintenance requirement

By virtue of the easy mounting arrangement and simple connection to an existing domestic hot water supply, the system is more cost effective, requires minimal installation time, no parasitic energy use, less disruption to existing Domestic Hot Water (DHW) supplies and offers a range of alternative mounting options (façade, DIY, apartment living, etc). Proposed capital costs of between one half and one quarter of traditional solar thermal systems will save up to 700kWh of energy annually. The University of Ulster is actively seeking industrial partners to develop this product further.

Advanced Vacuum Glazing has undergone development at the University of Ulster. Its role has evolved into that of a component of a double glazed unit and also into a triple glazed completely vacuum glazed unit and has been developed under EU, SFI, EPSRC, and InvestNI programmes. The advanced vacuum glazing is being actively considered for smart facades, enhanced solar thermal energy collection, lower energy refrigerated display cabinets as well as building retrofit applications. Demonstrations are currently underway as part of a retrofit package for existing houses as part of the EPSRC Consumer-Appealing Low Energy Technologies for Building Retrofitting (‘CALEBRE’) project.

The major project arising from the infrastructure development funded by the Department for Employment and Learning for Northern Ireland and the University of Ulster under the Research Capital Investment Fund objectives was the completion of “Terrace Street” opened by DELNI Minister Dr Stephen Farry MLA on 25 January 2012. “Terrace Street” was devised to allow the development of a refurbishment strategy that can demonstrate to all stakeholders the potential pathways and intended and unintended consequences of retrofitting a challenging housing type. “Terrace Street” consists of two solid wall dwellings originally built in Belfast in 1900. Pre-1919 solid wall types represent some 14% of Northern Ireland’s housing stock and therefore represent the greatest challenge in terms of retrofit.

Heat pump development has focussed on the development of higher temperature air to water units again focussing on their use in domestic retrofit applications. Collaboration with Emerson, EA Technical Services and other leading component manufacturers and again initially supported by InvestNI, the Carbon Trust, DELNI, SFI and EPSRC has seen the development of novel compressors capable of high efficiencies when heating hot water at over 60°C – a temperature that allows use of existing radiators and also satisfies hot water requirements. Therefore traditional fossil fuelled boilers can be replaced by high efficiency electric heat pumps, a role which, when coupled with energy storage, can provide domestic demand side management which will facilitate the integration of non-dispatchable wind energy. Such research is accompanied by test facilities and the skill-sets are currently being utilised to develop heat pump options for local, national and international organisations.

Energy storage is being actively considered at utility, commercial and domestic levels through the Centres market modelling and the development of small scale electrical and thermal energy storage system such as those related to phase change materials for thermal energy storage. Compact and highly efficient thermal energy storage can be utilised to ensure heat pumps operate at the lowest electricity tariffs for example. Such tariffs may ultimately be part of a smart energy grid future where large scale wind (and potentially wave) energy is managed in part by domestic heat pumps coupled with energy stores.

Professor NJ Hewitt BSc DPhil CEng CPhys MInstP MInstR MEI
Director, Centre for Sustainable Technologies, University of Ulster
Newtownabbey, Co Antrim, BT37 0QB Northern Ireland

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