Small Chinese Diesel Heaters

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Having had experience of diesel heaters installed in vehicles, They have drawbacks, I cannot see how they would heat your workshop to any value . I would vote you stay as you are, the cost of changing etc just does not appear to be worthwhile IMHP.
 
Beech - good to see you've crunched the numbers to make an informed decision, that landed around where I thought it would in terms of the relative benefits. Regarding some of the alternatives also listed, my own brief thoughts are:

-Air source heat pumps do give you some leverage in terms of making each unit of electricity do more work for you, but the coefficient of performance (or COP) is strongly temperature dependent. In summertime (where you can run some of these units as air conditioners) and at the beginning/end of the heating season (where your heat demands are low) the COP is generally quite good - sometimes as good as ~4 (i.e. 4kWh of heating for every 1kWh of electricity). In the coldest mid-winter months however (when you use the most energy), the COP drops off dramatically, sometimes being little better than just running an electric heater. Some units also suffer from icing on the external heat exchangers in really cold conditions; this is dealt with by temporarily heating the coils (running the pump in reverse) which is a further source of energy loss. I've never crunched the numbers myself, but my gut says whether ASHP's are a good idea depends on where you are in the country and what your winters are like. A mild south-west England winter they might be a good idea, if you're in the Scottish Highlands I would think less so.

-Ground source heat pumps give better performance because they absorb their heat from underground pipes (they are only a few feet down - it's not the same as traditional geothermal energy). Because the temperature just a few feet underground is much more stable year-round, the COP of these units isn't so dependent on atmospheric conditions and you get much more efficient mid-winter heating (still with the COP approaching 4 if you don't need high temperature heat e.g. ~35-40°C for under-floor heating rather than ~80°C for a conventional radiator system). You do however need a big area of ground to lay the pipes into (otherwise you just freeze the ground from trying to take out too much heat from a small area) and accept the disruption those groundworks bring. The scale of the installation also makes GSHP's very expensive to install.

-Solar thermal - is great for supplementing hot water demand, particularly in summer. As a method of space heating though it's terrible - solar gain in winter time is very low (which is why it's cold in the first place!) and the size of collector you would need to satisfy a significant heating demand is unreasonably large. Similarly for solar PV.

-Waste oil burners have been around for a long time in workshops; good if you have plentiful supplies of waste oil.

Brtone - you are suggesting that diesel heaters aren't up to much - what do you base that on? My own experience is that this type of parking heater is perfectly capable of keeping my garage warm even on a cold day in January. In my view, whether they are a good buy just hinges on whether it's the most cost-effective heat source (which is a case by case thing).
 
This discussion, with its mentions of heat pumps and alternative energy sources, has reminded me of a really good book I came across a few years ago. Written by a proper scientist, David MacKay, Regius Professor of Engineering at the University of Cambridge, it discusses lots of energy related topics with enough background information to be much informative than any journalist's attempts. The whole text is available for free at the website, https://withouthotair.com. Unfortunately it doesn't seem to have been updated since 2015, but I recommend it as a way in to the main concepts.
 
Yep, Professor MacKay's book is a great text for getting to grips with energy - accurate, accessible for the reader with limited scientific background but enough there for the technically literate to get their teeth into as well. Sadly the author was taken far too young and is no longer with us; everyone I've met who studied under him spoke very highly of him.
 
Rorschach":3t9toua5 said:
I'd be interested to compare Solar Thermal to Solar PV connected to an immersion heater.
When I installed ours (2006) I decided solar thermal was more viable for my needs. Since then I think this has changed. I have seen recent figures online that suggest themal is best if you want to get the most energy possible from a given area, but PV is better if you want to get the most energy from a given expenditure. So if you are constrained by space go for thermal but if you are constrained by finances go for PV. Is your roof bigger than your wallet?

Of course you could also compare the two on non-cost grounds and maybe arrive at a different answer ...
 
Rorscharch, gmgmgm,

One quick look at solar voltaic and thermal systems tells me they are a no go. They may be excellent but they are too costly. I would be looking at a minimum £7,000 to £14,000 to have these installed with no likelyhood of payback within a reasonable period. PV systems are also about to lose the Government subsidy/payback so look even less attractive.

My take on that is I would create an expensive set of systems which did not previously exist and from my cash. The power companies would take any overproduction and pay nowt. Seems to me that the Government and Energy companies are colluding to obtain something for free which they should pay for.

Anyway Solar is out of they equation for me.

Air-to-air heat source is still in the frame and even supplementing it with wood. An oil burner is also in the frame as a discussion with a local workshop identifies a problem they have with disposing of waste oil and ATF. Busy at the moment identifying the pros and cons of these as well as doing some of the math re costs. Again there is an initial investment of around £1000 to £3500 to consider.

I'll let you know about actual heat performance when I find out.

If you use air-to-air yourself then please comment on your experience.
 

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