In the UK, heating and hot water for buildings make up 40% of energy use and 20% of greenhouse gas emissions. These emissions must be reduced by over 20% by 2030, with a nearly complete decarbonisation by 2050, as part of the legally binding targets set by the Parliament in the Climate Change Act. To reach these targets and reduce the energy consumption, an innovative Versatile PCM (phase change material) energy storage system is presented. The proposed Versatile PCM system can play an essential role in synchronizing end use energy demand and supply on a short to long term basis. Versatile PCM will encourage the use of energy-efficient solutions, especially being adaptable to the British weather where the solar radiation may change dramatically during a day. Versatile PCM is a promising advanced technology in addressing the "heating on demand" energy issue in building applications. Apart from a possible modest loss of sensible heat just after charging, the thermal energy will be effectively stored at room temperature or ambient temperature, without loss, until required. When heat is required, a trigger is activated to induce heat release. Versatile PCM is an innovative and alternative energy storage measure with the advantage of controllable heat release and greatly reduced heat loss. To enhance long term energy storage at ambient temperature, installation can be placed as PCM groups, each with its own trigger, enabling release of heat only as demanded for long term needs. Normally, PCM can store heat with very high energy density, however, for long-term storage, heat loss is still a challenging problem. In conventional PCM storage, the PCMs are stored at ambient, above their melting point, resulting in continuous loss of energy. A major advantage of Versatile PCM is the use of the supercooling characteristics of PCM where heat is released only when the user triggers the crystallization mechanism, allowing long term, efficient storage. Photovoltaics/thermal solar collectors will supply a hot fluid to charge the PCM cells. The heat can be supplied to cells directly by the collectors in high solar radiation days and by the heat pump in low solar radiation days where the temperature of the heat transfer fluid can be boosted by a PV-driven heat pump. The system can also be implemented in industrial applications, where waste heat can be stored in the PCM cells and used later when it is required. Different numbers and sizes of PCM cells can be activated at different times to meet the heating demand. The flexibility in amount of heat release and available time of storage makes the Versatile PCM installation unique and especially suited to regions with high variability in weather conditions such as the UK. The system can be charged during high solar radiation days and the stored heat released according to heat demand on subsequent days. The novel technology developed through this project is much more efficient than traditional heating technologies by eliminating heat loss during thermal storage and being controllable in end use energy management, and therefore can significantly reduce the carbon emissions from the heating sector in the UK, if widely installed.

The latest report of Intergovernmental Panel on Climate Change (IPCC) 'Global warming of 1.5C' emphasises the need for 'rapid and far-reaching' actions now to curb carbon emission to limit global warming and climate change impact. Decarbonising heating is one of the actions which is going to play a key role in reducing carbon emission. The Committee on Climate Change states that insufficient progress has been made towards the low carbon heating homes target that requires immediate attention to meet our carbon budget. It is well known fact that the ground is warmer compared to air in winter and cooler in summer. Therefore our ancestors build caves and homes underground to protect them against extreme cold/hot weather. Geothermal energy pile (GEEP) basically consists of a pile foundation, heat exchanging loops and a heat pump. Heat exchanging loops are usually made of high density polyethylene pipes and carry heat exchanging fluid (water and/or ethylene glycol). Loops are attached to a reinforcement cage and installed into the concrete pile foundations of a building to extract the shallow ground energy via a heat pump to heat the building during winter. The cycle is reversed during summer when heat is collected from the building and stored in the ground. GEEP can play an important role in decarbonising heating as it utilises the sustainable ground energy available under our feet. High initial cost remains the main challenge in deploying heat pump technology. In the case of GEEP, the initial cost can be reduced, if the heat capacity of the concrete is improved and loop length can thus be decreased. This can be achieved by incorporating phase change material (PCM) in the concrete. PCM has a peculiar characteristic that it absorbs or releases large amount of energy during phase change (solid to liquid or liquid to solid). This project aims to develop an innovative solution by combining two technologies GEEP and PCM to obtain more heat energy per unit loop length which would reduce the cost of GEEP significantly. PCM has never been used with GEEP in the past, therefore obvious research questions that come to the mind are (1) how to inject PCM in concrete (2) what would be the effect of PCM on concrete strength and workability (3) how PCM would affect load capacity of GEEP as primary objective of the GEEP is to support structure (4) how much heat energy would be available (5) what would happen to the ground temperature surrounding GEEP (6) how much it would cost (7) whether it would reduce carbon footprint of concrete. We aim to answer all the above research questions by employing sustainable and environmental friendly PCM and impregnate it in light weight aggregates (LWAs) made with waste material (e.g. fly ash, slag, glass). There are three advantages of using LWAs made from waste: first LWAs will replace natural aggregate in concrete as natural aggregates are carbon intense, second LWAs are porous and light so they can absorb large amount of PCM and reduce the weight of concrete, third reuse the waste. Laboratory scale concrete GEEP will be made with PCM impregnated LWAs and tested under heating and cooling load to investigate thermal (heat transfer) and mechanical (load capacity) performance. Extensive experimental and numerical study will be carried out to design and develop novel PCM incorporated GEEP which can provide renewable ground energy for heating and cooling.

Through the 2008 Climate Change act, the UK committed to reduce by 80% its carbon emissions. While great progress has been made so far, data suggests that reductions in emissions have been achieved through switching electricity production to greener, more environmentally friendly sources, such as offshore wind. Clearly, it is inevitable that, to achieve further reductions in carbon emissions, we need to look for improvements elsewhere, such as heating and cooling of buildings, which accounts for 25% of all UK final energy consumption and 15% of carbon emissions. Project SaFEGround aims to provide a template for reducing emissions associated to heating and cooling through the deployment of heat pumps. These are efficient devices capable of extracting heat from a storage medium, e.g. air for air-source heat pumps or the ground for ground-source heat pumps, and this is done with high efficiency, since for each unit of electricity consumed by the system, it is usual to get 3-4 units of heat. Clearly, these are more environmentally-friendly than boilers as they require only electricity, which, as mentioned above, is increasingly being generated from renewable and low-carbon sources. Therefore, SaFEGround will investigate how ground-source heat pumps can be coupled with civil engineering structures to deliver low-carbon heating and cooling in a sustainable, safe and efficient manner. To achieve this, SaFEGround will combine research on material science, heat pump technology, energy geotechnics, building energy systems modelling, whole-system modelling and finance, to demonstrate that ground source energy systems can play an important role in the UK's future low-carbon energy mix in a cost-effective manner.