kWh From Flow rate, and difference in temperature(Solar Tubes monitoring)

graememk · 2022-09-26T23:33:56.777Z

Asking this in heat pumps because its what your doing here monitoring energy from a heat pump.

My solar tubes on my roof have no monitoring, Just the control board thats still working fine, dont want to annoy that, but we are planning on refilling it and also replacing the pump thats on it as its on its last legs.

As its going to be drained, I’m planning on putting a flow meter on it (pulse counting) and 2 temperature sensors… most likely just zip tied to it. for the temperature difference.

I could have swore I seen a calculation here (openenergymonitor) that calcuated the kW from the flow rate and temperature difference, But I cant find it, Or I’m not remembering what I actually need to search for.

A point in the right direction would be much appreciated.

Robert.Wall · 2022-09-27T10:28:43.248Z

graememk:

I could have swore I seen a calculation here (openenergymonitor) that calcuated the kW from the flow rate and temperature difference,

It’s standard physics, the specific heat of water is 4.18 kJ/kg K (at usual temperatures

So from that Power(kW) = Flow rate (l/s) × Temp.rise (°C) × 4.18

It works for electric kettles, immersion heaters and showers - given a bit of re-arranging.

graememk · 2022-09-27T11:44:06.005Z

Thanks, I shouldn’t be looking stuff up when tired at 12 am!

As it’s gycol mix the specific heat will be lower but other than that it’s good.

Then I can just use the power to kwh in emoncms to log it.