DCN May 2017 - Page 18

design & facilities Management an economic benefit and no complications with regards to resilience for data centre owners. Does it therefore follow that the source of waste energy (the data centre) has to be located adjacent to the facility or process that requires heating? Low grade energy The simplest way to redistribute what is traditionally still seen as low grade energy, (server air exhaust air temperature 28oC – 40oC, with cooling water return temperatures rising to 32oC) despite the shift in data centre operating parameters (ASHRAE TC9.9 – 4th Edition 2015), is to redirect the warm air to a building which requires heating. However, in accordance with the ERE metric requirements, this space shall not form part of the data centre operating facility, such as a battery room, as this would form part of the PUE metric assessment. The centralised ‘indirect’ air cooling systems, which have seen a recent uptake in the UK, use outside cool ambient air to cool the data centre air through an economiser or plate heat exchanger. These could also be utilised to provide a warm fresh air source to a building requiring heating. Clearly the adjacency of the data centre and heated building would need to be close to make this both economically viable and practical as it involves the transportation of air, which as we know is not a particularly efficient energy transfer medium. Moving beyond the immediate vicinity of the data centre, and in considering the recipient of this energy, its operational profile and the data centre location relative to these facilities. Most facilities, whether it be residential or commercial in the UK, need heating for large parts of the year, and some can utilise 18 | May 2017 ‘The simplest way to redistribute low grade energy is to redirect the warm air to a building which requires heating.’ heat energy all year round, such as swimming pools and a domestic hot water requirement in hospitals and hotels. Like other waste energy systems such as Combined Heat and Power (CHP) and Energy from Waste (EfW) it follows that there must be a potential heat sink, creating a thermal mass which can absorb and redistribute this energy in a controlled manner to where it is needed and at a grade at which it can be used. The latter two points are particularly relevant to data centre facilities, which operate 24/7/365 and traditionally produce low grade heat energy. District heating systems An obvious application and one that has seen some exploitation in the UK but a higher exploitation in the Nordic countries are district heating systems. Due to a long term decentralised energy approach in the UK, there is unfortunately limited scope in these systems in terms of load, number of recipients and geographical coverage on a town or city wide basis. In 2009 however, Telehouse, as part of its West Data Centre development, did make provision within the design of the facility to export waste heat to serve a number of homes in the Docklands area. In recent years the UK government, through Carbon Targets for residential developments, has encouraged the use of waste energy such as CHP and EfW. As a consequence there has been increased uptake in the use of common centralised heating systems employed to comply with planning and energy target requirements, with traditional gas boilers replaced by a high efficiency heat exchanger. The adjacencies of the ‘use’ and ‘source’ have therefore been driven by this demand, are relatively close geographically and consistent with dense population areas. The DoEE, in its promotion of CHP schemes, dedicate a webpage section to this. Various maps covering the whole of the UK are provided to highlight district heating schemes and thermal power stations, and show energy to waste and the potential heat load density – the latter being primarily driven by a residential need. These types of systems provide high grade heat energy as a primary or by-product of their process and generate higher value waste energy, as a derivative of a low fuel cost (Gas at 2-3p/kWhr). They also have high system efficiency, in which the waste heat output can be transported relatively easily either in a gaseous state such as steam ȁյЁ݅ѕȸQ)݅єЁ́ݕٕȁɥٕ)ɽɹɉ͕Օ)ȁ݅єѠݡٔ)ЁȁՅ)Q݅єЁɽф)ɔ́ɅѕЁ)ѕȁɅȁѡɽչ)ͽɍѥ̤ݡѼ͕ٔ)ЁɥЁѥѥ)ѥ́Ѽչɝمѥ)Ʌݡ́Ʌѥ)ٕѡɽ՝Ёյ̸)QɝɕեɕѼمє)хɽͽɍ)ݡ́ɔɉ)ɅՔѼٕ́ȁɕͥ)ɕ݅ѕи)Qѥѡфɔ)ЁѼݥѡɅѥ)յхѡɵ)ͥѡɴɥЁѥ)ѕ͕́٥ɝɕͥѥ)ɍѥ̰ݥɔ)Ʌѥɕ͔ѡ́Ք݅є)ЁͽɍU !@\)Ё́݅єЁѕѥ)ݡձͥ)ɥѽȁѼѡѥ)́ѡU,եѽ)ѕɉɕ