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Heating the Greenhouse, Sacing Energy

More Digging

Down to the plot for a couple of hours, still cold but not as bad as yesterday, where I dug over half of the large bed on plot 29. Incorporated the leafmould, compost and spent growbags etc in as I went.


I’m amazed at how the soil has improved since I took the plot on. Remembering how it was compressed and lifeless apart from the Horestail and how solid it was the first time I dug it, I think I can be quite pleased.


I was also rewarded as well! In digging it over, I came across a couple of pounds of quite decent potatoes I must have missed at harvest time. Managed to cut through the middle of a few more in the digging. I could have sworn I got them all aout.


Heating the Greenhouse


We have a lean to greenhouse on the back of my office here, about 6 feet deep by eight feet long. It’s made of wood and twinwall polycarbonate so holds heat well but we’re having some quite sharp frosts and I’d like to hold it frost free.


We have electricity running to the sheds which exits the office wall in the greenhouse so I have thought about fitting a plug. It would have to be the sort you can use outdoors as the greenhouse lets in a few drips. Anyway, I considered using a heater after this. I built a propogater that was powered with two lightbulbs and a frost thermostat but it was left behind in a house move. Remember a 100 watt lightbulb gives out 100 watts of heat. So, thinking I don’t need too much heat I looked at my options.


First, an electric heater. I could construct a small lightbulb heater for around a tenner, maybe fifteen with a thermostat and I do want to put power into the greenhouse at sometime.  Running costs for this would depend on how often it was on etc but electricity is no longer cheap.


Next option is a paraffin heater. Twowests do a small heater with equivalent to 120 watt output for just ten pounds – cheaper than B&Q. This would actually keep a coldframe warm and is probably enough to keep the chill off in the greenhouse except when it really drops.


Comparing the running costs is quite interesting. The heater takes 2.25 litres of paraffin and burns for 14 days. Paraffin costs around 75p a litre (less at our allotment shop) so would cost 1.69 to run for a fortnight. A 120 watt lightbulb would use 40.32 KW, which would cost, at 12.25p per KW, 4.94 pounds to run.


Save some money


Surprising how much a lightbulb can cost! Incidentally, if you use ordinary lightbulbs as against low energy bulbs, you are wasting a fortune. You are going to have trouble believing the figures below but they are correct. As they say ‘do the math’ or contact me and I’ll send you the long calculation.


A modern 20 watt low energy lightbulb lasts at least 10,000 hours and gives the equivalent of 100 watts of light. Assuming you pay 4.00 for the low energy bulb and 25p for a conventional bulb, which lasts 1,000 hours you pay 1.50 extra for the bulb. You save 800 KW of electricity over the bulb’s lifespan. At current electricity prices you save 98.00 pounds for your investment of 1.50. Better than the building society. And you help reduce CO2 emissions as well.


So for heating, paraffin and for lighting, low energy bulbs. You can get them in all sizes and shapes so you’ve no excuse.

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