Friday, January 6, 2012

Thinking about PCM again

5 Jan 2012: In the quiet times before the university term gets going, the imagination gets going to fill in the time and space. The Surya Sunbox system has been working splendidly, and still gets solar heat even in these wind speeds and temperatures. The thermal insulation and airtightness of the new construction has proved to be useful, at last.
But it is boring with everything working so well, what else can we do!? 
Wind turbine is out
I have tried thinking of every permutation, but what ever one thinks of is put off by our location. The only positions are on the south roof end, but that would shade our PV panels. At the north end, that would cause noise and coruscating shadow risk for our neighbours. It has been very windy today, but the tops of the trees were moving a lot, about 80 metres north of us, but around our house it was calm, due to the wind shading effect of Sharp Hill.

What about PCM?
I am thinking about this, especially as I have another skyscraper design project coming up, and we will again be considering the use of PCMs in that design. It would be great to have a mini prototype of the technology working here by the summer. I have been looking for wholesale Wax, but can only find it for candlemakers, and the like. Some companies are geared up to provide PCM products with precise phase change points. I have contacts
Article about PCM in World Architecture News,
See also, the link:
I would be interested in a small PCM store in the loft, and charge it up in the day to a higher temperature with heat from evacuated tubes, and discharge the heat to the borehole at night when the main Surya boxes are sleeping (using a time clock)

My more serious interest is the application to high rise buildings. I had students last year designing skyscrapers in New York.
See page 24 specifically. This was designed by three of my Masters students, with inspiration from the thermal storage ideas used on the Peveril Solar House - recognising that conventional borehole storage would be out of the question. The ground is 200m below, out of reach and is also blocked by underground car parking etc. So local storage with PCM would provide enough heat for the very well insulated apartments if heat was stored using high temperature collectors. This could provide enough for the entire winter, with topping up on sunny days through the winter, over very short horizontal pipe runs.

30 Jan 2012 Postscript: Ive been looking at the site of Rubitherm, a german manufacturer of just the sort of wax-based PCM that might be suitable. However.... as my present system runs at low temperature, it's not going to be a lot of use compared with the capacity of the soil under the house. I would love to use PCM creatively, but am still snookered.

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