Ground Source Heat Pump - NPV

Calculate Net Present Value (NPV) taking into account different operational costs, including capital, running, annual maintenance/replacement.
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Ground Source Heat Pump - NPV

Postby rossd01 » Wed Dec 14, 2016 2:52 pm

Hi Folks,

I'm wondering if you could help with some information as I'm working through the NPV calculation of a heat pump system.

IES VE has given me the heat requirement of my modeled multi-storey tower block as 181,133 kWh/year - this is the total heat that would be charged to all the residents collectively.

The electrical input to the heat pumps (CoP of 4.0) is determined as 45,283 kWh/year - this is the cost to me, in effect, to run the heat pumps.

Now, I'm beginning to confuse myself here when i try to remove the time element from these figures - at the moment, I am simply dividing by the total number of hours in the year, 8760. Considering the heat pumps alone (three in total, meeting a maximum demand of 107kW that occurs in January), this means i get a power requirement of roughly 5kW when I divide 45283 by 8760. But how could that be, when my combined heat pump capacity is far in excess of that? Would that therefore be 5kw per hour for the whole building? Have I just basically gone round in a circle by dividing by 8760?

Sorry...very confused! :/

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Re: Ground Source Heat Pump - NPV

Postby farahghanem » Wed Feb 15, 2017 9:39 am

you shouldn't divide by 8760 right off the bat. Firstly, your pumps will not be operating at peak "all the time", secondly your pumps do not necessarily operate 24/7 (i.e. every hour of ever day = 8760).

You can get the peak pump power from VistaPro, using peak day graph or synopsis.

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