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Need advice on solar hot, heat pumps or PV for my house

 
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Lord Beria3



Joined: 25 Feb 2009
Posts: 4058
Location: Moscow Russia

PostPosted: Sat Aug 05, 2017 5:25 pm    Post subject: Need advice on solar hot, heat pumps or PV for my house Reply with quote

I'm currently researching what type of alternative energy systems I would like to install on my south facing, semi-detached 3 bedroom house with a little garden.

Looking online, it seems that I have 3 realistic options;

1) air heat pump

The man I spoke to who works for the local electricity company recommended it as it is relatively cheap and would be well suited to my home (which is modern and well insulated).

https://www.renewableenergyhub.co.uk/heat-pumps-information/how-does-a-heat-pump-work.html#jump_61

Whilst it does rely on electricity it would make a significant impact on my overall heating bills.

2) solar hot water system - this seems the more simple and straightforward in terms of generating heat from the sun to power our water. However, does anybody have any feedback on whether it is the best course to take?

3) pv solar panels - pv systems where I live, based on current electricity prices, would take 25 years to "pay back". I'm also concerned whether pv's are sustainable in the longer term. I would like a alternate energy system which is isn't too reliant on exotic materials, high tech technologies that may not be easily available in 20 years down the line.

Would gratefully appreciate any feedback people can give on this subject!

My own thoughts are that it might be worth investing in a air heat pump and a solar hot water system which should seriously reduce my overall electricity bills in the long-term. Whilst I won't be self-sufficient or totally off-grid, I it would be a big step forward in my drive towards self-sufficiency and getting away from our decaying industrial systems.
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Lord Beria3



Joined: 25 Feb 2009
Posts: 4058
Location: Moscow Russia

PostPosted: Sat Aug 05, 2017 5:51 pm    Post subject: Reply with quote

http://www.resilience.org/stories/2016-12-29/a-leap-in-the-dark/

Quote:
JMG's guestimates on EROI costs of Solar Energy Systems (photovoltaic, reflectors and absorbers) and wind systems aren't a reflection of reality and more a reflection of his personal philosophy. Solar hot water heaters which are fully recyclable at low cost and have longevities of 50+ years if well built have EROI's better than 50:1. Photovoltaics can also be fully recycled into new product after their lifetimes are exhausted, if built once they are then reusable, EROI's are much better than most of the pessimistic forecasts but aren't as good as the optimists spruke, my calculations based on reused resources, not newly mined resources show EROI's somewhere in the 30:1+ range.


Does anybody know if the above stats are true?
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adam2
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Joined: 02 Jul 2007
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PostPosted: Sat Aug 05, 2017 6:24 pm    Post subject: Reply with quote

Heat pumps undeniably work, but may not be the best option due to cost, complexity and total reliance on grid power.

Thermal solar hot water works well if properly designed and installed, but is most unlikely to suffice in mid winter.

PV is worthwhile if grid tied, but is of course completely reliant on continuing availability of grid power. No standard system provides any protection whatsoever against power cuts.

Off grid battery charging PV is unlikely to worthwhile in strictly economic terms, but could be worthwhile as a doom prep.
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fuzzy



Joined: 29 Nov 2013
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Location: The Marches, UK

PostPosted: Sat Aug 05, 2017 7:20 pm    Post subject: Reply with quote

I would have thermal hot water pumped via PV into a heat exchanger in a tank. This tank would be the pre-feed ie cold into any gas boiler or could be tapped directly eg for a wearedodgy tap. This would give water warm enough to wash up in a power cut, or have a strip wash a bit above ambient temp even if it is not genuinely 21st century hot. It would save gas bills by pre-warming the water.

I would then install a couple of piezo ignited balanced flue wall heaters eg baxi in key locations downstairs. This will keep your house warm in a power cut. It's not about saving the world it's about saving your sorry ass in what is coming.
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clv101
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PostPosted: Sat Aug 05, 2017 10:44 pm    Post subject: Reply with quote

We were planning on using a wet solar system for hot water but have dropped that idea, instead relying on PV electric water heating (along with wood stove boiler).

The key reason for this is the 'use it of lose it' nature of off-grid PV.

Basically, whenever the solar thermal would be generating a good output it's likely we'd have several kW of surplus PV which can be dumbed through an immersion heater. Since we have the PV dimensioned for winter demand, there's surplus infrastructure for much of the year.

The solar thermal infrastructure is not trivial; in cost, complexity, or ongoing maintenance.

All that said - we are getting a thermal store with a 2nd heat exchanger in it to facilitate the possible addition of solar thermal in the future.

Air (or ground) source heat pumps are fairly pointless in the UK if you're on mains gas. Gas is a good deal cheaper than electricity so there's no (economic) point in using 1kWh of electricity to generate (say) 3 kWh of heat... when the electricity is three times the price of the gas in the first place.
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BritDownUnder



Joined: 21 Sep 2011
Posts: 208
Location: Hunter Valley, NSW, Australia

PostPosted: Sun Aug 06, 2017 11:23 am    Post subject: Reply with quote

I have all three systems in Australia and think they are all of benefit.

Air Source Heat Pump

I have several of these in individual rooms for air heating and cooling depending on the time of year. Surprisingly I would estimate that in Australia i still use them more for heating than cooling but i think that is probably due to my house being designed to stay cool at all times of the year. i find them very good with the house coming with one installed when i bought in 2011, which is very inefficient (I estimate a COP of about 2) and stubbornly refuses to die despite being about 15 years old. I had two smaller newer versions installed, one of which suffered a failed card after 5 years and a small 3/4 hp Fujitsu unit which has been a real stand out performer drawing less than 200 watts as a heater overnight and is quiet as a mouse.
Overall beneficial but could need a lot of spare parts in future and difficult to repair on your own.

Solar Water Heater System

In the high Australian summer this provides an excess of hot water (my record tank temperature was 86 degrees celsius) by being at far too shallow an angle due to incompetent installers. In winter I estimate it provides about half our hot water heating. in terms of kWh of electricity saved it saves about 6-10 per day in good weather and when raining is virtually useless. When I lived alone in one year I needed to put on the electric immersion heater on about 5 days per year. Now with family we have the immersion heater on about half the year.
Due to previously mentioned installers it should have been larger (30 vacuum tubes instead of 15 and a larger water tank 400 litres not 250) and put at a much steeper angle to catch the winter sun more square on.
My system requires a pump which will invariably break one day. It has been going for 6 years so far without problem.

Solar PV

The stand out performer and a 5kW system has turned a $2000 a year power bill into a $500 a year power bill for a $10000 initial investment and, along with insulating my house has made the place more comfortable in both summer and winter. 5 years so far with no problems. In terms of kWh generated i generate all my power but of course cannot use it all at the exact times i generate it.

All in all I would get all three on any new house I would move into. If I built a house I would try to make it as passive as possible and insulate well. I would try to avoid the pump on the solar hot water making it a thermosiphon type system if possible.

I have thought about Sanden CO2 (working fluid) heat pumps for heating water and radiator heating but is probably not really needed in Australia with a well designed house.

I have also thought about a inter seasonal thermal store but in an existing house is probably a non-starter.

In the UK I would think that all three would be less useful but the installation costs may also be lower. I guess I would start with a well insulated house before I did anything else.

The words of Joseph Tainter spring to mind when he says that to become more sustainable societies sometimes have to become more complex. Not always a good thing to get three quite complex systems in your home when a bit of passive design and insulation will be of more benefit.
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Potemkin Villager



Joined: 14 Mar 2006
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Location: Narnia

PostPosted: Sun Aug 06, 2017 7:52 pm    Post subject: Reply with quote

BritDownUnder wrote:


When I lived alone in one year I needed to put on the electric immersion heater on about 5 days per year. Now with family we have the immersion heater on about half the year.



Laughing One good job interview question I was once asked was about how energy efficient and sustainable I had managed to make my own personal affairs. The answer was that whilst I had achieved reasonable levels whilst single (living in a multi occupancy shared house) this had slipped somewhat after I was married and slumped even more significantly after we had two children............

As far as doom preps are concerned I know several folk who have worn out and had to recycle several small off grid wind turbines and battery stores over the past 30 years or so waiting for TEOTWAWKI.

I possess several PV panels and accessories which I sincerely hope I will never need to deploy.
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emordnilap



Joined: 05 Sep 2007
Posts: 13676
Location: way out west

PostPosted: Wed Aug 09, 2017 10:03 am    Post subject: Reply with quote

Solar thermal hot water is brilliant, even where I am in rainy Ireland. Mine's a Solartwin system which was dear but the basic idea and components are top class.

You can build your own version at a fifth of the cost of Solartwin and the guy that supplies the parts is one of the most helpful and knowledgeable people you could buy from. Have a look here: http://solarproject.co.uk

I've no ties to his company apart from getting incredibly good advice from him.

At his prices, it makes no sense to not have SHW. On ordinary, not sunny days, raising the temperature of your cylinder water by even a few degrees adds to the 'payback' - and you get at least a few degrees practically every day.
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Lord Beria3



Joined: 25 Feb 2009
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Location: Moscow Russia

PostPosted: Thu Aug 10, 2017 8:20 pm    Post subject: Reply with quote

All, thanks for the feedback.

Will take it on board.
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emordnilap



Joined: 05 Sep 2007
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PostPosted: Fri Aug 11, 2017 10:17 am    Post subject: Reply with quote

Potemkin Villager wrote:
I know several folk who have worn out and had to recycle several small off grid wind turbines and battery stores over the past 30 years or so waiting for TEOTWAWKI.


Yes, unless you're technically or practically minded, maintaining 'doom preps' ( Laughing ) is not easy.

Hopefully it'll become part of a handywoman's or man's job to do simple maintenance and repairs of these - alongside the cleaning gutters, power-washing drives, window cleaning, etc that white van people do.
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adam2
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PostPosted: Fri Aug 11, 2017 11:09 am    Post subject: Reply with quote

I wore out a Rutland wind turbine when living in London, but suspect that it had paid for itself in terms of energy produced. So no waste of money.
I wore out several sets of batteries, but most were acquired for nothing anyway.
Part of being prepared is IMO being able to generate your own electricity and store it in batteries, these cost money and need regular replacement.

The O/P enquired primarily about money saving and fuel saving preps for use whilst BAU continues. Grid tied PV for example, and heat pumps can be valuable in this respect but are totally reliant on continuing grid availability.

Solar thermal hot water is often grid reliant for pumping, but not always, some systems use gravity circulation or a PV powered pump.

It is wise to make preparations for a future with higher energy prices and a much reduced income.

It is also wise, IMHO, to prepare for a future without utility services. Such preparations cost money, not save it. Look upon the expense not as an investment that produces an income, but rather as an insurance policy.
A modest sized battery bank that needs renewal every 5 years is an insurance policy, not a money saving investment.
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Potemkin Villager



Joined: 14 Mar 2006
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Location: Narnia

PostPosted: Thu Aug 17, 2017 12:54 pm    Post subject: Reply with quote

adam2 wrote:


The O/P enquired primarily about money saving and fuel saving preps for use whilst BAU continues. Grid tied PV for example, and heat pumps can be valuable in this respect but are totally reliant on continuing grid availability.


Grid tied PV is also totally reliant on finding a use for energy produced with a mid day peak or obtaining a lucrative export deal. This is an example of a very poor PV deal :-

https://www.electricireland.ie/residential/products/smarter-living/solar-pv?_ga=2.76661845.1507959910.1502970617-1106140754.1500887200

One of my holiday home neighbours with much more money than sense is currently having "spin the job out" contractors installing a geo thermal heating pipe network under his front lawn. Unless he also installs underfloor heating or much larger radiators I think he will be quite disappointed at the performance of the system considering the outlay.
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emordnilap



Joined: 05 Sep 2007
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Location: way out west

PostPosted: Thu Aug 17, 2017 2:34 pm    Post subject: Reply with quote

Potemkin Villager wrote:
adam2 wrote:


The O/P enquired primarily about money saving and fuel saving preps for use whilst BAU continues. Grid tied PV for example, and heat pumps can be valuable in this respect but are totally reliant on continuing grid availability.


Grid tied PV is also totally reliant on finding a use for energy produced with a mid day peak or obtaining a lucrative export deal. This is an example of a very poor PV deal :-

https://www.electricireland.ie/residential/products/smarter-living/solar-pv?_ga=2.76661845.1507959910.1502970617-1106140754.1500887200


Yes. That's Ireland for ya. Very high per capita emissions (Eurostat places us third highest in EU) but little action to remedy that.
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