Solar / renewable hot water and heating

avoidtheupsidedownbottles

MWT said:

The Bunsen Air Heat Exchange System is essentially a reverse refrigerator circuit...

It looks like it might suit a scenario like an Alpine ski resort where the air temperature is very low but there is year-round direct sunshine.

matelodave

Both my fridge and freezer are noisier than my ASHP and I can hear my neighbour's oil boiler from across the road (only installed a couple of years ago) so ASHP's aren't as noisy as some people like to make out. Granted the big fans (2) do make a bit more noisy when the wind is in the wrong direction but I have to put noisy ear to the casing to check if the scroll compressor is running.

BTW did anyone notice my previous mistake - 4500/85 = 52.9 rather than 5.9 so this magic machine could take 30-40 years to pay back if it was just producing your hot water. However looking at the test data, it's assuming that it's being used to heat a hot water tank in a domestic environment and so only drawing off around 120-to 180 litres a day what would happen if it was used to heat a buffer tank and then also provide continuous hot water for say 12-14 or even 24 hours a day when heating a house and providing hot water as well. I guess you'd need a lot of supplementary heating

TBH for the outlay that the OP is proposing I'd be inclined to look at a proper solution using an ASHP or GSHP

MWT

tigertedd_2 said:

(although there are of course more lucrative ways to invest £20k over 20 years, so I'm very reluctant to use the term 'a good investment'), but it's certainly not a bad or money loosing investment.

Compared to other investment opportunities it is a terrible choice, but you aren't doing this as an investment so I'd stop kidding yourself on that one

I'm not going to try and persuade you one way or the other, but from what I've read so far I'd be asking some more questions about the required maintenance frequency on the Bunsen system, cost of recharging the refrigerant if required etc.

Also availability of parts keeping in mind that this is a novel solution with one manufacturer so you have no certainty that they will even be in business in 12 months time, never mind 25 years...

Ask about the the noise from the pump/compressor which I suspect is going to be running quite often if you intend to use it for more than just hot water. It should be low level but it is going to be noise inside the house unlike most other ASHP solutions...

avoidtheupsidedownbottles

From the icons next the solar collector, presumably it also acts as an air-source exaporator when the sun isn't shining.  Be interesting to know if it compares favourably against a solely air-source system in that mode.

MWT

avoidtheupsidedownbottles said:

...  Be interesting to know if it compares favourably against a solely air-source system in that mode.

Badly I would say, as it appears to be an entirely passive device.

You would have to expect the night-time performance to be limited as the temperature gradient will be much lower at night with just ambient air temperature to warm the refrigerant and no forced airflow. 

Like matelodave above, I'd be looking to compare it to a normal ASPH system which doesn't have the risks associated with this somewhat unique solution.

Gerry1

On a cold winter's night, do you end up with an iceberg crashing through your roof?

matelodave

avoidtheupsidedownbottles said:

From the icons next the solar collector, presumably it also acts as an air-source exaporator when the sun isn't shining.  Be interesting to know if it compares favourably against a solely air-source system in that mode.

No ever so well I'd guess as it's designed to collect radiated heat from the sun rather than getting a good ariflow over it to collect low grade heat from the surrounding atmosphere.
 I'm sure it works pretty well in sunlight but not when there isn't and that's when you need most heat if you are going to use it to supplement your heating system.

Ignoring COP figures if it doesn't produce as much heat or hot water as you require then you'll have to get it from another source which the \OP is suggesting will be electricity. I dont know what sort of solar set up he's got but that wont produce as much as he needs (unless its a big one) and he'll need quite a bit of battery storage to keep it going overnight or when the sun isn't shining.
 
As I said, it will need very careful sums to work out the heat requirements of the house in kwh and add that to anything else that uses leccy and try  to work out where it's all coming from and how its going to be used.

We can easily get through 50-60kwh of leccy a day in the winter, even with a heatpump which could easily equate to 100kwh/day or more using other forms of heating (gas, oil, storage heaters or solar power) so the calcs should use kwh as the common denominator and then translated to the cost and method of producing all those kwh.

avoidtheupsidedownbottles

MWT said:

avoidtheupsidedownbottles said:

...  Be interesting to know if it compares favourably against a solely air-source system in that mode.

Badly I would say, as it appears to be an entirely passive device.

You would have to expect the night-time performance to be limited as the temperature gradient will be much lower at night with just ambient air temperature to warm the refrigerant and no forced airflow.  

Yes and I suppose the requirements of a solar panel versus AS evaporator are diametrically opposite: one wants to be insulated from the surrounding air while the other wants maximum heat exchange.  Interesting that they appear to claim it does work at night anyway.  But yes Elephantboys post confirms it doesn't compare well it would seem.

avoidtheupsidedownbottles

matelodave said:

No ever so well I'd guess as it's designed to collect radiated heat from the sun rather than getting a good ariflow over it to collect low grade heat from the surrounding atmosphere.
 I'm sure it works pretty well in sunlight but not when there isn't and that's when you need most heat if you are going to use it to supplement your heating system. 

Sorry, missed your post.  Sounds like it won't be too useful beyond daylight use, at the very least.

tigertedd_2

avoidtheupsidedownbottles said:

matelodave said:

No ever so well I'd guess as it's designed to collect radiated heat from the sun rather than getting a good ariflow over it to collect low grade heat from the surrounding atmosphere.
 I'm sure it works pretty well in sunlight but not when there isn't and that's when you need most heat if you are going to use it to supplement your heating system. 

Sorry, missed your post.  Sounds like it won't be too useful beyond daylight use, at the very least.

I don't get it. From reading the gum, it sounds like it just needs to be warmer than -26C in order for the refrigerant to boil and therefore create energy. Liquid goes in, gas comes out. So it doesn't need direct sunlight. The installers have even said there's no need to put it on a south facing wall, as it really doesn't matter if the light shines on it, it's just about the ambient temperature of the air.
Not got any vested interest in defending it (other than I'm quite keen to get one, so I'm probably biased towards kidding myself that the numbers add up), but I'd hate to to be judged on the wrong metrics. The whole point of this system is that it works at night, otherwise, it might as well just be a solar hot water system.