Wednesday, March 17, 2010

Value Engineering thoughts

17 March: It would be good if this system can be repeated, more cheaply, so that the technology could be simplified and adopted. Some Value Engineering needs to be done to quantify the benefits, against the possible installation costs of a system, materials and labour. For the benefits, this are many variables depending on the existing location, eg south facing or shading, depth of existing boreholes, heat loss of the house, operating regime and existing energy costs of the occupants etc. And the benefit may not simply be in the bills - it can reduce the installation capital cost of a GSHP. If it can reduce the depth of a borehole from 100m to 50m, that is saving about 2000 pounds! It might be able to remove the borehole altogether enabling one to charge up a horizontal array of underground pipes. For installation, there is the layout of the loft, the difficulty of laying and insulating pipes through the house to the heatpump. Rightly so, there is a higher skill factor in working with glycol than your average house water supply system. There is a design cost in adapting the system to fit the house shape and orientation and complexity of layout.
   In the early days of heatpumps, they were strictly experimental, and it has taken a long time for them to be accepted as a heating system that can be widely used (we have to thank the Swedes, Austrians etc for this, it would never happen in the UK!). It could take a while with this, if the penny pinching approach was to "not bother unless the cost is lower than... "
   This "Solar-Air GSHP augmentation system" (which it might be called) must have as a basic requirement, the black panels (the cheapest part), and the metal mounting rails... the Polycarbonate, and metal framing is essential for extending its usefulness deep into the winter, to increase the Diurnial benefit (in case Interseasonal benefit is unknown or a vain hope).
  Piping can be replaced with smaller diameter or even plastic hosing. Insulation is essential to avoid condensation, and its cost is proportional the the lengths and diameters involved. The pump is essential, and the energy flowmeter is essential for testing and proving, even for a simplest installation (you would not instal a PV system without letting the customer see what was being generated - the same applies here). The differential thermostat is essential. The solenoid valve is not, although it is a minor cost. It must have a design element because every house is different - windows, overhanging roofs or nearby trees all have to be taken into account. There is scaffolding. The labour cost has to take into account the amount of climbing about in the loft by the plumber, and the construction work on the outside.
   If we find that a lot of heat escapes and doesn't get recovered, there would be no point in increasing the number of black slabs from 4 to 6, and it is clear that the thermal harvest from just 2 panels would not be enough to justify the cost of the piping, scaffolding, flowmeter, pump etc. (I talk in Twos because of the symmetry of the movement of glycol through panel - but even numbers are not essential). So the system as I have built it seems to have been a good judgement.

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