Solar Heating - grant aid and advice?

meadowcat

mrmister wrote:

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Perhaps a few others could joing the debate rather than leaving it to a few to do it's a public forum over 6400 views only 80 something comments- Anyone care to join in?

'Tis with fear and trembling I join this discussion. Oh such heated debate. I will only state the facts of my experience with SWH. I will not enter into any argument.

I have had my SWH panel for just over one year. It cost me, after grants, just over £1600. It is a German made Schuco panel, professionally installed by a great company - definitely not of the "cowboy" type so often talked of on these forums.

I have kept a very careful record of my electricity usage. In the year since the panel was installed, I have used 1200 units less than the previous year. My electricity is 11.6p (NIE) per unit. I'm sure you can work that out yourselves.

I cannot say how much oil I have saved as I would find this impossible. What I do know is that I get hot water even in the winter, therefore the hot water tank is pre heated, so I would accept that I don't use as much oil as I would have previously. If any of you can work that out, feel free.

I live in a 2 year old bungalow, just under 2000 sq feet. I would estimate that in the last year I have used about 1200 litres of oil, but that may not be anything to go by as everyone has personal preferences in relation to the amount of heat they like in their house.

The worst day for solar is very overcast and raining. In that year I probably had about 5 or 6 disappointing days. I have had temperatures of over 40 degrees when there is snow on the ground.

That's my experience over the past year. Take it or leave it. Like I said, I am not going to get involved in any arguments such as lost interest on initial outlay - no matter how much I am goaded!!!:rolleyes:

mrmister_3

Thanks meadowcat for joining the debate with some hands on experience, hold no fear
I hope that no one else is fearful I certainly don't wish to make anyone fearful from my part i'm sure others would agree, all on topic views are definately welcome.

I am interested in the setup of your system, if I may; Were you, are you using electric heating or oil prior to the solar and are you supplementing your solar hot water with elelctricity or oil if it isn't up to temperature? are you using a solar cylinder or a thermal store? What temperatures did you acheive on the disappointing days? Finally what part of the coutnry are you in (for a take on the solar energy falling in your area)

meadowcat

mrmister wrote:

I am interested in the setup of your system, if I may; Were you, are you using electric heating or oil prior to the solar and are you supplementing your solar hot water with elelctricity or oil if it isn't up to temperature? are you using a solar cylinder or a thermal store? What temperatures did you acheive on the disappointing days? Finally what part of the coutnry are you in (for a take on the solar energy falling in your area)

mrmister, I have oil heating, but pre SWH I would have used immersion heater for hot water is the summer when heating was not on, although I would only have put it on for short periods to get hot water for dishwashing or household cleaning. I think my biggest saving on electricity is that I am using my solar hot water for my dishwasher and washing machine.

The company I used installed a larger cylinder with a thicker foam type covering, a control panel and an expansion tank in the hot press.

The disappointing days I referred to were days when I had no solar gain whatsoever - dark, overcast days. The pump does not start until the temp at the collector is 5 degrees above the temp at the bottom of the tank. It goes off when the difference is 3 degrees. So, if the water is still hot from the day before, the temp at the collector needs to rise above it by 5 degrees to start pumping.

If I need hot water for dishwashing etc and the heat from the solar panel is not enough, I would still use the immersion heater, but as the water is already partially heated, it only takes a couple of minutes to get enough hot water. I can honestly say in the past year I have only had to do this about half a dozen times.

I am in Northern Ireland. (that's why my electricity is so expensive.:mad: )

Cardew

meadowcat wrote:

I have kept a very careful record of my electricity usage. In the year since the panel was installed, I have used 1200 units less than the previous year. My electricity is 11.6p (NIE) per unit. I'm sure you can work that out yourselves.

I

Meadowcat,

Obviously a saving of 1,200 units @ 11.6p is approx £140.

For those of us lucky enough to have gas it would save £24 to £36pa

Why do you not use oil CH to 'boost' your DHW instead of the immersion heater? It would be much cheaper than electricity at 11.6p per unit.

mrmister_3

Meadowcat how many in your household?

It may be possible to work out the oil used if you have kept previous bills simply compare before you had the solar to bills now.

From how you described your system I don't think the cylinder is operating as a thermal store in the sense I mean, that is:
The cylinder is connected as part of the heating circuit, there is no store of hot water. A coil within the cylinder heats the cold mains incomming water either directly or outside of the cylinder through a plate heat exchanger. Both would be thermostatically mixed to provide a fixed temp draw off. Therefore the store is the heat source for the hot water indirectly and heating directly. The reverse of conventional cylinders.

Cardew

mrmister,

I do appreciate my approach on this matter is somewhat confrontational – although I prefer your “open and frank” terminology!; and if that offends you then I apologise.

I agree with your suggestion that we come up with our estimate of costs and savings, for a 10 year period, in a separate post and I will put mine at the end of this post.

Firstly a comment on this link you posted as it has been discussed and discredited previously. It is illustrates perfectly the modus operandi of the alternative energy industry that riles me. I don’t know if you read it thoroughly?


http://www.energie-cites.org/db/belfast_140_en.pdf


It is produced by an organisation with the grand title of Belfast Energy Agency who are simply an organisation who sell solar systems. Their ‘study’ is several pages of methodology and data but when you look at it closely there is no scientific study at all. Data, and I use the term in its loosest possible connotation, is taken from householders and all savings that they(and you) quote boil down to this significant statement:

Based on information from householders, who recorded oil savings of 1000 litres of oil per annum,

Now the calorific value of heating oil varies but all types I believe produce over 10kWh per litre.

I believe we have agreed that the average house uses 4,000-5,000kWh to heat DHW. So at 50% efficiency we are looking at savings of 2,000- 2,500kWh.

So miraculously these households supposedly saved 1,000 litres of oil which is over 10,000 kWh of energy. Which would indicate they use 20,000kWh heat their hot water – 400% to 500% more than average!

These ridiculous figures are seized upon and quoted as if they are some authoritative source. For example, in your post you have used these figures(in bold print) to quote a saving of £340pa.

Cardew Estimate

Installation costs

I accept your figure of £625.97 per year for 10 years a total of £6,259.70

Estimated Savings
My estimate is current savings of £60pa – using gas CH
I will accept your estimate that energy prices will rise by 10% each year for the next 10 years(although I hope you are wrong!)

Thus the savings over 10 years will be £956


Perhaps you will post your projected savings.

meadowcat

mrmister, 4 in house. As this is a new house and we have only been in it 2 and a half years, I would find it difficult to assess the saving in oil.

I do have details of dates and quantities of oil purchased right from the start. However, I don't care how scientifically someone works it out, it would be impossible to give accurate figures from one year to another as no-one uses their heating for exactly the same number of hours per day and the same number of days per year. Also, is there a device that will show with total accuracy how many litres you have used? What I do know, is that I have more oil in the tank now than I had at the same time last year.

I do not understand the thermal store you are mentioning. My SWH is purely for hot water and has nothing to do with actually heating the house - other than the fact that, as the hot water tank is already heated, the oil boiler has less work to do. The new hot water tank which was installed is twin coil. One for the CH and one for the SWH.

peat

It is my understanding that a Thermal Store system consists of a store of water at high temp (80 degrees centigrade or so) directly connected to the CH radiators with hot water coming from the mains and passing through a heat exchanger coil. Since the Thermal Store is meant to be kept at or near optimum temperature by the power source (oil, gas, electric or whatever) when would it ever get cold enough to be "topped-up" by solar?

mrmister_3

peat wrote:

It is my understanding that a Thermal Store system consists of a store of water at high temp (80 degrees centigrade or so) directly connected to the CH radiators with hot water coming from the mains and passing through a heat exchanger coil. Since the Thermal Store is meant to be kept at or near optimum temperature by the power source (oil, gas, electric or whatever) when would it ever get cold enough to be "topped-up" by solar?

Well you are almost correct. But the primary heat source would be solar not the oil gas or electric. These others would only heat the store if there were no solar available and the store required heating.

A description of a thermal store.
When solar energy is available and the solar pump is activated, the store is
heated when a temperature measured at the take off from the panel is
appropriately higher than the set point in the store. The ultimate temperature in the store is limited by an electronic limit thermostat within the unit. The solar heat
exchanger in the store is located in such a way that even small amounts of heat
from the panel can be utilised.
The significance of the store is that water pre-heated by the panel,
even in Autumn, Winter and Spring can be fed through a conventional gas or oil
fired central heating boiler and this limits the energy required for heating. Direct
hot water is always immediately available to be drawn off and takes benefit from
solar input whenever it is available through the very high efficiency heating coil in
the normal way. If large volumes of direct hot water (DHW) are drawn off the
controller will assess whether the conventional boiler needs to fire to ensure
ultimate customer convenience.


NOTE: solar stores work on stratification in the water levels and hot water rises and cooler sinks therefore while the top of the tank will reach 80c or higher the res of the tank is varying degrees below this. The heat for the heating system is taken midway down the store and the solar coil would be right at the bottom. A solar cylinder is tall and narrow in design with correctly positioned coils of the correct spec. A normal cylinder is not in the same country let alone ball park.

This is important, it is ridiculous to not use a proper cylinder designed for solar, anyone having quotes for solar heating should be suspicious of an installer not specifying a solar designed cylinder (be it a thermal store or a twin coil such as meadowcats etc). Yes it will work but you'll reduce your efficiency and really you'll be throwing away your money simply to usitilise a cylinder not designed for the job yes you can poke a pipe in a cylinder and it will work, but it won't work efficiently and does it comply with Water regulations is it approved? I haven't seen one yet -That's my view.

meadowcat wrote:

I do not understand the thermal store you are mentioning. My SWH is purely for hot water and has nothing to do with actually heating the house - other than the fact that, as the hot water tank is already heated, the oil boiler has less work to do. The new hot water tank which was installed is twin coil. One for the CH and one for the SWH.

In that case the oil boiler would be contributing to the heating of DHW and it would be unreasonable to suggest the only saving is in the Electricity used.

meadowcat wrote:

"I have kept a very careful record of my electricity usage. In the year since the panel was installed, I have used 1200 units less than the previous year. My electricity is 11.6p (NIE) per unit. I'm sure you can work that out yourselves."

as in the colder months it is possible the controller is progrmmed to fire the boiler for DHW also, perhgaps meadcat would clarify, I believe this makes sense as meadcat feels there is a saving in the oil used above that expected for not heating the house as much for instance.

Cardew-

Thanks. I will spend a while reading through and answer you more fully later, I wasn't aware the history of the belfast study perhaps we should discard their data if it has proven unreliable - can you post me some links to read through on this? Yes I did highlight those figures to make a statement and provoke more research. (I admit I haven't had as much time as I would like to read everything thoroughly) I came across several studies that were unconvincing I guess I didn't digest that one enough.
How about the other study i found? there are very few to work from perhaps you can find some from here? http://www.managenergy.net I must go teach now. Would be good to see some more input from others with experience in this field practical as well as theoretical.

Cardew

mrmister wrote:

Cardew-

Thanks. I will spend a while reading through and answer you more fully later, I wasn't aware the history of the belfast study perhaps we should discard their data if it has proven unreliable - can you post me some links to read through on this? Yes I did highlight those figures to make a statement and provoke more research. (I admit I haven't had as much time as I would like to read everything thoroughly) I came across several studies that were unconvincing I guess I didn't digest that one enough.
Would be good to see some more input from others with experience in this field practical as well as theoretical.

mrmister,

Regarding other links.

I don’t know of any ‘scientific’ projects with independently verified data on solar heating for domestic households.

There are so many firms masquerading as quasi-official organisations in this field. If you read their ‘blurb’ it is full of statements like “savings up to” or “some customers claim savings of ”. As far as I am aware none of these firms will guarantee an output for their systems. Also despite their claims of longevity, the systems are not backed by other than a 2/3 year guarantee.

The problem in getting objective evidence on actual savings from customers is most of them are not prepared to admit in public that they have paid several thousand pounds for a system that just doesn’t deliver. That said there are hundreds of claims for misrepresentation waiting court appearances and I doubt if there is a Trading Standards Authority in the country that hasn’t issued warnings about the scams going on – do a Google.

I am aware of 4 people on this forum who have solar systems and have provided us with some data. (I have made assumptions on the gender of these contributors)

paul_h, who seems quite an expert, inherited a system and calculates that it saves him £60 a year.

meadowcat has a system that has a realistic max claimed output of 2,000kWh(which very much supports her contention that her installer is not a cowboy). Last year she saved 1,200kWh on her electric bill(her oil CH switched off in the summer) and presumably there might be some oil saved during the winter. Difficult to quantify how much, but let us assume that the max output of 2000kWh is achieved. That, for those with Gas CH, means a saving of less than £60pa.

yakky58 has only fairly recently installed his solar system and in May reported “that Gas consumption is now 30% of what it was for heating water.” It is difficult to extrapolate estimated savings from that statement. Clearly more in the summer and less in the winter. So 50% of the average annual consumption would appear an reasonable assumption - £60-£75pa

simonm of Solar Kent has given us the most comprehensive data. (Solar Kent have some connection-an agent??- with Genersys plc who install systems)

His monthly totals of saved energy are recorded and show that his system produced an annual total of 4,434kWh. What is surprising is that 90% of that total was produced and used between April and October – it is difficult to see how most people could use that amount of hot water in that period. Therefore one must deduce that he uses approx double the average amount of DHW.

Even so his savings for the full amount of 4,434kWh would amount to £130pa.