Friday, January 20, 2012

Tubes, high in the sky

20 Jan 2012:  Another reason for my interest in Evacuated Tubes is that they will contribute to my Skyscraper interest, because I am envisaging high rise facades which can include these, high in the sky out, of the way of trees and adjoining houses, optimally angled and positioned.
   I would have to rethink my ideas on thermal storage, as the cost of the PCM required for a winter's storage for an entire apartment is excessive. My colleague Dr Boateng is ordering some of the same tubes from Kingspan this month because he is doing research into tubes with PCM storage.
   For short term use, Water is the best store, but once it is hot, it reaches stasis (and has other problems, such as evaporation). One reason for liking PCM is that it absorbs more and more energy without getting hotter. But cost is an issue.
Heron Tower, Bishopsgate, London
I don't think it is practical to have arrays of tubes transporting heat directly to a ground store 200 metres below during the day time - system losses would be too serious. But it is practical to have daytime energy transferred to large water stores at intervals up the building. Energy is immediately available for local Diurnial heating and DHW that same day to the apartments in the floors near the tank. During the night hours, surplus energy is purged to a deep underground store in extremely well insulated ducts for later retrieval. (rather like the Norwegians pumping water uphill to lakes to cope with surges in hydro-electric demand).
   Tall buildings need deep caissons, and it is even possible to consider that the caisson is built, with insulated edges (but perhaps uninsulated bottom), tubes are laid, and much of the fill is returned (instead of being transported off site). For an insulated ground store, the sizing of the store would be very important because it is finite. There is less demand for underground parking now in major cities like London, so the caisson (which is still needed) can have a purpose.
   Under the Heron Tower in Bishopsgate, London, there is a caisson, but for reasons of traffic management, they only have a small handful of parking spaces, the majority being for disabled access. (I've no idea what they do with the remainder of the basement, but tall buildings usually require storage, loading bays for service, M and E plant.).

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