Harvesting Heat from a Heat Pump

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Our electricity bill is becoming an object of fear and loathing. 
So we talk about alternative solutions such as solar water heating, geyser blankets, timers, gas and other options.
Water heating is by far the single biggest expense on our electricity bill … commercial or residential, so it makes sense 
to focus our attention here … before we get into hot water so to speak!
One high-tech solution I keep hearing about is the Heat Pump.
Heat pumps, of whatever variety, give you the giddy feeling of breaking the laws of physics. 
A gas boiler is 80 percent efficient.
An electric heater is almost 100 percent efficient. 
But a heat pump can be more than 100 percent efficient. 
A 1000-watt electric heater emits 3400 BTU of heat in an hour, but the same amount of electricity, used to run a heat 
pump, might transfer 15000 BTU of heat into your geyser.
The trick is that a heat pump moves heat rather than generating it from scratch. It’s basically just an air-conditioner 
working in reverse. 
Heat pumps scavenge and extract heat from the outside air. 
This heat-laden air, even on cold days, is solar energy—it’s just another form of it, and this is what gives heat pumps 
the edge in terms of super-efficient heating appliances.
It pumps hot water straight into your geyser and switches off when the desired temperature is reached.
No matter how cold it gets out there, in South Africa there’s always some heat to harvest, although the task gets harder 
the colder it gets. 
By avoiding the production of ‘new’ heat, a heat pump transcends the so-called ‘efficiency limit’. 
It still takes energy to run, but the mechanical energy (used to circulate and compress a refrigerant) generates a highly 
efficient thermal result.
In simple terms a heat pump consumes a low level of electrical energy to achieve a high level of heat energy.
By installing a Heat Pump it is possible to reduce the total electricity consumption in your home by
approximately 30%


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Roger Metcalfe is a freelance journalist specializing in the environment, technology and medicine.
He is an ex-diplomat, and former TV documentary producer (environment).
He currently runs his own solar energy business “Solar Connect”.
He also produces corporate films and is reading for his Masters in Filmic Communication.
He can be contacted at roger@solarconnect.co.za

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