stonehouse, page-2

It's not the bellows that need firing up (actually, it's the bellows that DO the firing up): the problem is, I think, the cooling.

If you look at the investor presentation of 1 June 2012 (any one will do though, they're all pretty much the same) you'll see that the water that cools the refrigerant enters the cooling tower at 37C and leaves at 25C. Obviously, to cool water to 25C, the cooling tower itself must be cooler than 25C, let's say at the most 22C.

Here are the temperature records for Carnarvon:

http://www.weatherzone.com.au/climate/station.jsp?lt=site&lc=6011

A straightforward heat exchanger is not going to work for most days, and even some nights, of the year. When I spoke to Peter yesterday he said that the wet bulb temperatures were good for the cooling. This means that the cooling tower itself is supplied with water which the refrigerant water evaporates. This takes much more energy from the refrigerant water than just ordinary heat exchange. Peter said that the tower can use up to one cubic metre of water per hour. That is 1,000kg of water which , with a latent heat of evaporation of 2,270kJ/kg, means that the cubic metre can absorb 2,270,000kJ/hr from the cooling water.

So, how much heat does it need to take out? The Opcon Powerbox Brochure (it's a pdf file, Google "Opcon Powerbox Brochure" it should be the second site) uses a flow rate for the recirculating cooling water of 700 cu. m/hr.

The specific heat capacity of water is 4.2kJ/kg/C

So to cool one kg down by 12C we need to remove 12 x 4.2 = 50.4 kJ/kg.

700 cu m = 700,000kg, so to cool THAT down every hour by 12C we need to remove:

700,000 x 50.4 = 37,800,000 kJ/hr.

Presumably the cooling tower is designed to cool the 700 cu m/hr with a low ambient temperature, but I can't see how it can do it in Carnarvon's climate as the evaporative element can only take out about 7%.

I asked Peter how much water the tower was expected to use, and he was reluctant to put a figure on it - but clearly, if it can only use 1 cu.m/hr, it can't use enough. And when the atmosphere is very humid, it won't work anyway as the water won't evaporate.

So even if the plant gets commissioned now, in winter, when there is a chance of there being enough cooling for it to run at nameplate, I can't see how it can work anywhere near capacity in summer.