Energy calculation

Dear All,

Can anybody advice me how to calculate electrical energy consumption by just measuring chilled water flow to the consumer and temperature difference?

I believe in the district cooling plants they are doing something similar but not sure.

Thanks in advance.

Regards,
KRA.

Specific heat of water ( 1 calorie per gram - degree) times temperature difference times flow rate will give you power (energy per unit of time). Beyond that you need to know something about the efficiency of the chiller to get any meaningful data about electrical energy usage.

kra101 said:

Dear All,

Can anybody advice me how to calculate electrical energy consumption by just measuring chilled water flow to the consumer and temperature difference?

I believe in the district cooling plants they are doing something similar but not sure.

Thanks in advance.

Regards,
KRA.

Click to expand...

It depends on what level of accuracy you are after. You can calculate the mechanical energy (hence power) using Bernouli's equation (example at http://www.engineeringtoolbox.com/mechanical-energy-equation-d_614.html). But to convert this to a useful electrical energy figure you would need to know the the power curve, power factor, and efficiency of both the pump, motor and any VSDs connected to it. This is not a trivial amount of work for a plant of any size.

If you're only interested in a relative measurement (i.e. how much has the power consumption changed over, say, a week) then you have nothing to lose by giving it a go if you have the time to spend. However, if any kind of accuracy is important, then I'd suggest adding power monitoring to your motor cabinet. These systems are not too expensive, and give very useful information on where the power is being consumed in your system.

Steve & Binaural,

Thank you very much for your advices.

Regards,
KRA