Heating a greenhouse

[pigletwillie]

Thanks all,

I seem to have it stable at around 12 degrees, which should be enough to keep things going, there is also thermal gain on sunny days which we had yesterday and today which saves on the leccy

[Helen]

Now for some maths! just to give you an idea how to work out how much something costs to run

Appliance wattage "Divide by" 1000 "X" Time on = Units used

example of 3kw heater

3000 "div" 1000 = 3
"X" 10 (10hrs) = 30 units used

Price per unit will depend on who your supplier is so have a look at your leccy bill but as an example mine is 8.8p during the day & 3.4p on the economy 7

so in theory my heater would cost me £2.64p to run for 10hrs on the day rate, obviously this is not the case as the heater is not on for 10 hrs solid, you can by special meters in Maplins that you plug the appliance in & that tells you exactly how much you use
Hope that is of some help

[nog]

In Parlementary fashion. Mr Speaker I refer to my previous answer "Ouch" Thats £30.66 a week. Ok if you are using a 1kw heater thats £10 if it is on all week. I think I will stick to my paraffin at 3 bottles a month. Which is about £3 per week.

[Helen]

I see what your saying although if it was on only half the time thats only a fiver & the leccy is "On Tap" as it were no trips out to buy the parafin so there probably is not a huge amount in it

[pigletwillie]

Hi Helen,

I took meter readings for the three days before firing up the heater, and took an average, the difference 2 days later is about 70p a day more. To cover this I have put my rather large pond pump on a timer so its only on for 12 hours a day now so the cost difference is negligable.

I really wanted a minimum temperature to keep things growing but not make it too warm that stuff romped away too fast.

[Youknowwho]

Quote:
a bit of frangrance always clings to the hand that gives roses
So does a bit of muck

[Helen]

Hi Piglet!

70p isn't bad, I think what we all have to remember is that gardening is a hobby & when we have a hobby we spend money on it, its not like paying the leccy bill for the household things, we need to think of it as paying towards something that we enjoy doing after all Do we give the price of a gardening magazine £3.50p a thought when we buy it? probably not but in leccy terms thats 5 days worth & if your like me I buy several mags, monthly & weekly ones & in total I probably spend not far off the same money I spend on leccy to heat the greenhouse(frightening thought) I'm not starting my heater off for another week or two so I will cost up mine & see if its comparable to yours, my greenhouse in 6x10 & I have a 3KW heater

Helen

[Allan]

Darren, thermal storage is a far better bet than solar electric panels, there is a huge inefficiency gap on solar electricity for heating as the best only give about 5% conversion. Wind power is too fickle to depend on and not cheap either.
Allan

[richard p]

allan, i am confused why does the efficiency of energy conversion with solar power matter if the sunlight is free and renuable

[richard p]

should have added . its the initial capital cost of the "free" energy sources that is the problem , not their conversion eficiency

[Allan]

Exactly so, Richard. An output from a 15 watt solar panel is going to cost about £100 for the panel, you need a lot of those to do anything much for you. Compare that with the incidental rise in temperature of a water butt, hosepipe or anything else left in the sun for a few hours, it's a totally different magnitude. Maybe a visit to C.A.T. would sort you out on this one, but you can find a lot out from their website.

[fen not fen]

Try fresh chicken manure for a free if smelly source of heat - I came by a disused deep freeze with a glass top, and filled it with fresh chicken muck. The rapid decomposition of the muck creates heat for free. I've also heard of people doing the same with straw bales with a bit scooped out and chicken muck added.

[sue-the-recycler]

Darren C and others are on the right track - Whatever the fuel used, good insultation is the number 1 priority, raising the staging a few inches (or lowering the roof) can make a huge difference even the site of the house itself can make a difference. I use 8 hour night light candles in a metal trough under the staging as a boost in really cold weather - cheap and simple

[Tigger]

Don't forget agricultural bubble wrap. You can get a big roll of this from your farm suppliers for a reasonable price. I use it to line my tunnels, construct my inner chamber (see previous postings) make individual tents - whatever. I bought a monster roll in 2003 and am still only half way through it with two tunnels, an acre of veg and an acre of fruit.

[richard p]

just thinking aloud really, how about a plastic tent or box with some high wattage lights. the light would help the plants grow and the heat given out should warm a couple of cubic meters of air?