Navitron Renewable Energy and Sustainability Forum

BIOMASS => General => Topic started by: Fiddlers on August 17, 2009, 11:20:37 PM



Title: Biomass for DHW & Heating with solar - lots of questions!!
Post by: Fiddlers on August 17, 2009, 11:20:37 PM
Hi all, I'm in the process of buying a grade II listed Victorian semi in deepest Dorset and top of the list of things todo is the heating.... it's about 80m2 over 2.5 floors, total about 190m2 and currently heated by radiators fed from a gas Rayburn running from small Calorgas bottles!! Loft insulation is "reasonable" (looks about 100mm), mostly new double glazed windows, but solid walls. We tend to be at home most of the day.

I've been doing lots of reading around the biomass subject over the last few weeks and have a system in mind that I'd appriciate comments on. We'd like to be as green and spend as little money on heating as possible. So, a wood boiler seems the sensible way to go. Don't mind a bit of manual work (we have two growing boys who can be persuaded to help!!) and have lots of space for log storage.

Because the building is listed and I don't fancy the boiler and associated gubbins in the house I'm planning to install it in a detached garage, about 5m from the house. My thoughts on equipment are a 25Kw gasifying boiler, 1500 or 2000l accumulator, Ladomat, etc. I already have a Navitron 20 tube solar kit that I'm planning on installing on the garage roof (east/west facing so would probably get another array to get the most sun possible). For connection to the existing heating system in the house I'm planning on using pre-insulated 4 core underground piping (hot+cold DHW + heating flow/return). I'd like to do most of the install myself - I'm reasonably DIY competent, with help from a friendly plumber for the tricky parts.
What I'd like to achieve is a system that requires max 1 burn/day in Winter and purely running on solar in Summer for DHW. So, here goes with the questions!
1. Has anybody managed to install a 1500/2000 litre accumulator (probably Akvaterm) in a garage? it's fairly large (9*4m) with a 30degree roof pitch. I'm thinking that a 2.2m tall tank will protude into the roof void and will require the trusses to be modified. Given that I'd like to keep it an open vented system for simplicity, the header tank will be immediately above the accumulator - will that work? I'm planning on a DHW coil in the accumulator for mains pressure water. On that subject, are there many problems with having a closed system? I've read about anual certification of the pressurised parts?
2. Chimney height - I've read that 10m is quite normal. That could be tricky! again, anyone with experience? We're quite low but not much shelter.
3. Solar panels.... Given the tank size there's no way a 40 tube east/west array is going to heat it. Most of the accumulators seem to have an optional solar coil at the bottom of the tank which seems wrong to me. Surely a coil near the top of the tank, such that the top portion only is heated would be better. Given that solar will only be useful in the summer when heating isn't required I'm essentially only using the top area of the tank for DHW. I guess I'd need valves to stop heat escaping from the tank through the solar array in the Winter of course. Anyone else have a similar set up or am I worrying about nothing?!
4. If it all goes horribly wrong can anyone recommend an installer in the Blandford/Sterminster Newton area? :-)

Many thaks all, it's been great filling my brain with this Forum!!

Regards,
James


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: Brandon on August 17, 2009, 11:40:27 PM
too tired to go into it now, but you will need that garage at least full of logs every year to come close, and they will need to be PROPERLY dry, so you will need to store twice that amount.

The heating required with wood is no less than that required with gas.

insulate insulate insulate

Then worry about heating.

If you will not be allowed to insulate, don't buy it, it is not too late judging from your post.

edited for spelling...


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: dhaslam on August 17, 2009, 11:58:07 PM
I assume the detached garage already there. You could drop the floor level as necessary  in the area of the boiler and the storage tank and   fit  a tall tank comfortably in the increased  headroom   It would also give more chimney height for the boiler.    

Given the very variable pattern of sun strength the big storage volume and plenty of tubes makes a lot of sense but you need to be able to store heat without significant losses for several days and this needs serious levels of insulation. Older houses  need heat for longer periods of the year and  there are probably  days  between  March and  May,  particularly,  when there could be enough heat from solar to heat the house.  You can get very tired of fueling a large woodstove  and there is always the feeling of producing CO2 and using up forests.   It would be nice not to have to light the stove sometimes.    


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: Fiddlers on August 18, 2009, 08:45:17 AM
too tired to go into it now, but you will need that garage at least full of logs every year to come close, and they will need to be PROPERLY dry, so you will need to store twice that amount.


Thanks for the comments... I'd use the existing garage to just house the boiler and tank and enough wood for about a week. There's a seperate covered log storage (probably about 10m3 currently and could easily be enlarged). Completely agree about insulation and I'm including that in the rather large job described as "sort heating" at the top of the todo list!!  :D

Regards,
James


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: Fiddlers on August 18, 2009, 08:51:55 AM
I assume the detached garage already there. You could drop the floor level as necessary  in the area of the boiler and the storage tank and   fit  a tall tank comfortably in the increased  headroom   It would also give more chimney height for the boiler.    

Given the very variable pattern of sun strength the big storage volume and plenty of tubes makes a lot of sense but you need to be able to store heat without significant losses for several days and this needs serious levels of insulation. Older houses  need heat for longer periods of the year and  there are probably  days  between  March and  May,  particularly,  when there could be enough heat from solar to heat the house.  You can get very tired of fueling a large woodstove  and there is always the feeling of producing CO2 and using up forests.   It would be nice not to have to light the stove sometimes.    

Interesting ideas... I wasn't assuming I'd get any heating benefit from Solar, just DHW in Summer. I can imagine doing a burn maybe once a week in Spring/Autumn just to assist the solar.
Dropping the garage floor may well prove simpler than messing with the roof construction! The other option would be to build a detached boiler house but I'd almost certainly need planning given the height requirement and don't want the delay & cost really. Food for thought - thanks!

Regards,
James


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: billt on August 18, 2009, 09:58:50 PM
What you are suggesting is perfectly feasible. I have a 2500l Akvaterm accumulator and Atmos 25kW gasifying log boiler in my attached garage and am intending to install a lot of solar panels to provide heat in the spring / summer / autumn. It is a flat roofed garage with sufficient clearance for the store.

The header tank needs to be above the highest point in the system, so if you have radiators on the top floor of your house, the header tank needs to be higher than that.

Certification only applies if the cylinder is pressurised, a mains pressure coil is OK.

My flue is currently 7M, which I hope should be OK, although the Atmos boilers seem to need a lot of draught.

To get a useful amount of heat into a large store, you are going to need lots of panels. I intend to install 8 30x58mm tube solar panels, and that still won't give any useful hot water in the winter. It's probably more sensible to have a separate, relatively small, cylinder for hot water which can provide usable hot water for more of the year with a smaller solar array.

Having the solar coil at the bottom of the store should mean that you extract as much energy as possible from the panels, although it won't produce hot enough water.

Do you know what the heat requirement of the house is? That is a prerequisite before you start designing a heating system like this.

Do you have a completely reliable and reliably cheap source of wood? If you don't I wouldn't contemplate an expensive, labour intensive system of this sort. Calor gas may be expensive, but it doesn't need much input from you; processing and handling wood gets tedious very quickly for most people and if you don't own the source is likely do get expensive as well. Calor gas is also a pretty unpolluting fuel, certainly cleaner than wood.


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: billi on August 18, 2009, 10:34:45 PM
Quote
Having the solar coil at the bottom of the store should mean that you extract as much energy as possible from the panels, although it won't produce hot enough water.

I wounder ,how( and know some do it)  to utilise the low temperature the solar panel produces in winter/cloudy days better. A small heatpump plumped in to the solar cycle and let the solar preheated water be boosted  sounds like a good idea to me

Ok off topic , but  seems sad to see a solarpanel producing some power but not allowed into the thermal store , cause too cold  :-[

Billi


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: Fiddlers on August 19, 2009, 12:01:35 AM
What you are suggesting is perfectly feasible. I have a 2500l Akvaterm accumulator and Atmos 25kW gasifying log boiler in my attached garage and am intending to install a lot of solar panels to provide heat in the spring / summer / autumn. It is a flat roofed garage with sufficient clearance for the store.

The header tank needs to be above the highest point in the system, so if you have radiators on the top floor of your house, the header tank needs to be higher than that.

Certification only applies if the cylinder is pressurised, a mains pressure coil is OK.

My flue is currently 7M, which I hope should be OK, although the Atmos boilers seem to need a lot of draught.

To get a useful amount of heat into a large store, you are going to need lots of panels. I intend to install 8 30x58mm tube solar panels, and that still won't give any useful hot water in the winter. It's probably more sensible to have a separate, relatively small, cylinder for hot water which can provide usable hot water for more of the year with a smaller solar array.

Having the solar coil at the bottom of the store should mean that you extract as much energy as possible from the panels, although it won't produce hot enough water.

Do you know what the heat requirement of the house is? That is a prerequisite before you start designing a heating system like this.

Do you have a completely reliable and reliably cheap source of wood? If you don't I wouldn't contemplate an expensive, labour intensive system of this sort. Calor gas may be expensive, but it doesn't need much input from you; processing and handling wood gets tedious very quickly for most people and if you don't own the source is likely do get expensive as well. Calor gas is also a pretty unpolluting fuel, certainly cleaner than wood.

Great to hear from you!
How often do you need to do a burn, and what's your heat requirement?
According to http://www.resurgence.org/resources/heac.html the heat requirement is about 42000 kWh currently. I'd like to think I could get that down to about 34000 without requiring planning for exterior wall coatings - which tbh I don't fancy anyway since they will ruin the character which is why we're buying the house in the first place. We might be able to dry line some of the interior walls which would help more. Just for fun, the EPC in the HIP pack shows current energy rating as an 11, with potential for 12  ::)
I'll be honest and say I don't really understand what the header tank is there for! I thought because the heating is pumped that'll provide the pressure to drive the water through the rads, and mains pressure water through the heat exchanger in the accumulator will provide ample DHW to the house at good pressure.....dunno, I feel I'm missing something obvious :) I know there needs to be expansion for the accumulator too. Can that be a sealed pressure vessel?
Using a separate tank for DHW for Sunny use seems the sensible way to go. I guess the plumbing becomes a bit more complicated with having to have valves to switch between tanks, but much more usable. Especially given the only sensible sighting for panels is east/west so I'm not expecting 100% from them.
As for costs, I'm willing to take the hit on labour to detach myself from the volatility of fossil fuel prices. Installing a full sized Calor gas tank may be an option, but just doesn't seem the right thing to do. There's plenty of woodland and sawmills in the area and we have a family tree surgeon, so I'm guessing supply won't be a problem but I will make sure before taking the plunge. Good point, well made!
Whatever I do, the current 13Kg gas bottles and 1980s Rayburn are going!

Regards,
James


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: Brandon on August 19, 2009, 10:03:46 PM
from my experience, the price of wood follows the price of oil, as if you can get more for it, why not?


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: kristen on August 19, 2009, 11:39:59 PM
"Has anybody managed to install a 1500/2000 litre accumulator (probably Akvaterm) in a garage?"

I've got a 2,500L Akvaterm (and another 2,500L plain-Jane tank alongside it) in my garage.

Couple of thoughts:

If doing it again I would find a way to put it in the house.  The standing losses are about 10C per day, I'd prefer that was going into the house (at least during the Winter!) than the garage.  The garage also has a much greater Delta-T than the house (its nearly as cold as outdoors) which aggravates the problem.

Watch out for the tipping-height to get the tank upright. That will be greater than the standing height.

There is a loading hook on the top of the Akvaterm - if space will be tight, after bringing the tank vertical, take that out first!! (And fit anything like a  top air release thignie before up-righting it too)

"Given that I'd like to keep it an open vented system for simplicity"

Why?  Mine has a direct, pressurised, non-open vented link from Boiler to Store. I then have a further circuit (still direct/pressurised) to a heat exchanger where the old boiler used to be.  This transfers heat to the original CH circuit which is open-vented - I don't suppose its old, corroded, pipes would withstand pressurisation.

Consdier whether your DHW circuit will have any problems with mains-pressure how water (if currently using an open-vented hot water tank).  A power shower here didn't work when given mains pressure.  Also, do the fill-a-bucket and time with a stopwatch to see what your mains pressure is like.  Repeat using two taps and two buckets - twice the time, or less than that [less is good!]

"I'm planning on a DHW coil in the accumulator for mains pressure water"

I have two DHW coils in my Akvaterm.  One very low down "preheats" the DHW, and the "primary coil", right at the top, tops up the heat as required.

This means that the maximum heat is withdrawn from the bottom of the tank - which reduces the amount of heat removed from the top, which in turn reduces the thermal currents, and helps maintain stratification (i.e. keeps the top of the tank hot, and the bottom of the tank cooler)

I then have a mixing valve to deliver max. 60C into the DHW (we have very long pipe runs, 60C is about right to get  a decent temperature at the point of use).

"I've read about anual certification of the pressurised parts?"

My installer didn't mention it  whistle

"Chimney height - I've read that 10m is quite normal."

Mine is pretty tall (not 10M though, I don't think).

I saw a massively tall stainless chimney on a straw-burning (farm 2000) boiler recently.  They had bricked around it, and it almost looked like it has always been there! (I'll attach a picture)

"Most of the accumulators seem to have an optional solar coil at the bottom of the tank which seems wrong to me. Surely a coil near the top of the tank, such that the top portion only is heated would be better"

My advice would be to heat the tank "as little as possible" - i.e. maintain as low a temperature as possible.

A piece of sound advice I was given was along the lines "Getting the tank to 60C is easy, getting it to 70C and above is harder"

I have two solar coils, one at the absolute bottom (so the coldest water is always available to be heated by the solar), and the other is about 1/3rd from the top.  The TDC3 controller treats the bottom coils like a heat dump - i.e. when the top of the tank is at 60C then all heat goes to the bottom.

So the top of tank is heated to 60C, which guarantees hot water, and then all subsequent heat goes to the bottom.  Once the bottom is at 60C too the heat continues to be delivered to the bottom and the whole tank temperature rises - but more slowly that if the top was heated to, say, 70C first. However, with a pre-heat DHW coil in the bottom of the tank that heat lower down is still harvestable.

"I guess I'd need valves to stop heat escaping from the tank through the solar array in the Winter of course. "

Don't think that's an issue.  A NRV should prevent thermo-syphoning (in fact the TDC3 will give you an error report if thermo-syphoning happens at night etc,)

"Anyone else have a similar set up or am I worrying about nothing?!"

You are definitely not worrying about nothing. This is pioneering, not shrink-wrap, and my recommendation is that you gather all the data you can before making the jump.

One issue will be the ratio of solar panels to thermal store.  2000L is big - I think 5L / 42mm tube is the yardstick, or 7.5L per 58mm tube. So 2,000L suggests 400 x 42mm tubes, or 266 x 58mm tubes.  I have 180 x 58mm tubes facing due South.

The risk is that with a small solar array you get a tank of tepid water :( However, with two coils the top part of the tank is prioritised, and that should work fine. But if the top of the tank is, say, 750L then you still need 150 x 42mm or 100 x 58mm tubes.

And you will lose 10C standing loses from the WHOLE tank :(

Alternative is to heat an additional smaller DHW store and use the main, larger, Store as a heat dump.  You can still have a pre-heat coil in the Store to use whatever heat is available there first. (You implied that you think this adds complexity, actually I think its pretty normal.  Twin coils is common, and the controller takes care of it, you just need a motorised valve [which should be on the return].

"a 25Kw gasifying boiler"

I have a 60kW gasifying log boiler.  It burns for 4 hours. I calculated that we use about 240kWh of heat a day in the depths of Winter.

240kWh per day in depths of Winter for as few months as possible (i.e. coupled with a "generous" solar thermal system which can help in Spring / Autumn [the fact that it is oversized for Summer is solved here because I have a pool :)] I have equated that to 20 cu.m. of bone dry wood (to emphasize what Brandon said - bone dry is crucial, otherwise you need a lot more wood as lots of its calorific value is spent on driving the water out of the wood to start with!).  Don't rely on my figures as I have not yet gone through a full winter with this setup, but it may help as a yard stick or a useful check against your own figures- Tell me if you come up with a radically different value please!

"The heating required with wood is no less than that required with gas."

Can't speak about Gas, but the Wood I am buying (green, to split and season myself) is 1/3rd the price of oil [if I have got my calculations right for the amount I will need].  Not to mention that we have the occasional tree that becomes caput, and the local tree surgeon occasionally drops off a load of Leylandii that he would otherwise have to pay to dump.

I have lived in a number of large houses, and I have found that getting the thermal mass up to temperature is key.  I don't know if this applies in your case, but our approach has always been to set the morning heating to 2 or 3 degrees above the rest-of-day comfort level. That is reached by 8am, and maintained until around 10am, and then the thermostat "falls back" a couple of degrees; most Winter days the heating doesn't come on again until the evening. I've never thought the big houses that we lived in needed a lot of fuel (relatively speaking).

"There's a seperate covered log storage"

You need to store 3 years fuel supply, ideally (unless you are buying seasoned wood, in which case good luck to you - rogues abound in that market!)

"I wasn't assuming I'd get any heating benefit from Solar, just DHW in Summer"

Solar insolation in December is about 10% of that in June. So you will get some ... and the joy of having a shared Thermal Store is that it all counts! And every kWh of Solar is one less of burnt wood.

"I can imagine doing a burn maybe once a week in Spring/Autumn just to assist the solar."

Don't forget the standing losses.  You can heat the thermal store up to 85C, but it will decay quite fast.  Before we installed the Solar we ran the boiler twice a week (just for DHW).  (We need 30kWh per day for DHW, we use the same number of Litres as an average family, but twice the kWh compared to a gas boiler, because our pipe runs are long AND taking into account the standing losses of the thermal store)

[In our case we did a half-burn because in the Summer we had disconnected one of the two thermal stores].

"Do you know what the heat requirement of the house is? That is a prerequisite before you start designing a heating system like this."

I agree. We ran our oil boiler for 2 hours morning, and 2 hours evening (it didn't have any sort of thermostat would you believe!).  If we were cold at lunch time we pushed the one hour boost button. So that gave me a good feel for the fact that we were running the boiler for 4 hours a day (same as with my log boiler) . Some sort of comparative metric like that is useful, but I had a heating engineer make some thermal calculations too.

"Do you have a completely reliable and reliably cheap source of wood?"

My experience has been that most suppliers see signs when you talk about 20 tonnes of wood, and they quote for their normal small trailer (same as they deliver for folk that have the occasional open fire during the winter).  Mostly they were talking 140 / tonne (or cu.m or whatever equivalent unit they were using - opinions vary :( ).  Anyway, I bought seasoned wood (for first season) at 70 / tonne delivered, and green wood (to split and season myself) at 40 / tonne.  Shop around, obviously.  Helps if you live in the countryside of course.

"the price of wood follows the price of oil"

I think that is more true of Wood Chip / Pellets, than logs; having said that about 25% of the 40 / tonne I pay for green wood is the haulage charge.

If you live anywhere near Suffolk let me know - you are welcome to come for a look-see and a chat.

Threads about installation of my systems are here:

60kW Log Batch Boiler and 5,000L Thermal Store Project Report (http://www.navitron.org.uk/forum/index.php/topic,5875.0.html)
    
6 x 30 tube 58mm Panel Project Report (http://www.navitron.org.uk/forum/index.php/topic,8251.msg87452.html#msg87452)




Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: kristen on August 19, 2009, 11:42:13 PM
P.S. Consider retaining your existing boiler, or a modest replacement using the same fuel, as an additional heat source to your thermal stoe.  Useful to have an automated boiler when you go away ... or perhaps to keep the house warm if you break a leg and can't cart wood ...


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: Terrier on August 20, 2009, 12:09:59 AM
Hi Fiddlers,

Take a look at wood pellet or wood chip boilers, they will give you the low carbon result but with the automation of an oil or gas system, if you have local saw mills and tree surgeons, wood chip will be readily available at a very good price, you will need a fuel store, but you may get away with a "shed type" building which may not need planning permission, do not worry about a sealed system, as long as all the safety systems are in place it will make thing easier with the design of your heating system i.e. header tank feed and expansion pipes etc. you will also get away with a smaller buffer tank with a pellet or chip boiler due to the control of the boiler.

I know that you would like to to it your self, but I would recommend that you look for a Hetas registered installer as with all due respect by your own admission you do not know much about wood heating!
and this will ensure you comply with the building regs. for the future if you look to sell the house.

Terrier.


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: kristen on August 20, 2009, 12:36:35 AM
My 2p-worth is that Wood Pellet fuel will move with oil price.  As oil increases more people will install wood pellet boilers.  That will mean that we have more demand than the ability to make pellets - until someone builds a new factory.  Price will be the control at that point ...

I seem to remember issues with wood chip - moisture perhaps?  Something that made it less desirable as a fuel??


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: wookey on August 20, 2009, 01:42:40 AM
Lots of good advice from people with real systems there. Kristen - you might like to clarify your '10C' standing losses. Standing losses really should be in kW rather than degreesC :-)

Here's a bit of info from a theorist: Read the works of Simon Furbo on combi-systems. Lots of good info on mistakes to avoid, the importance of stratifcation in stores and factors making for more efficient systems (e.g. one big tank rather than several smaller ones). The only problem with this info is that there is a real dearth of large stores including statifiers for finite amounts of money. But I'd look at some of them (Solvis, sailer, consolar, capito, wallnoefer, solar plexus) as well as akvaterm. The tank is the core of the system that everything else is designed around. I found the Rebus Phd document fascinating too.

There really should be a 'useful theory docs' wiki page I could point you at, but you'll have to search the forum.
here are some useful threads:
http://www.navitron.org.uk/forum/index.php/topic,3411.html
http://www.navitron.org.uk/forum/index.php/topic,2281.html
http://www.navitron.org.uk/forum/index.php/topic,3857.html




Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: kristen on August 20, 2009, 07:31:35 AM
"you might like to clarify your '10C' standing losses. Standing losses really should be in kW rather than degreesC :-)"

Indeed. (I calculate that it is about 29kWh for my 2,500L store)

However, I think that 10C loss from a thermal store, per 24 hours, seems to be common? If that is so I think its a useful metric as folk can multiple tanks size x 10C and get kWh [for their system size]


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: Fiddlers on August 20, 2009, 09:03:37 PM
Hi Fiddlers,

Take a look at wood pellet or wood chip boilers, they will give you the low carbon result but with the automation of an oil or gas system, if you have local saw mills and tree surgeons, wood chip will be readily available at a very good price, you will need a fuel store, but you may get away with a "shed type" building which may not need planning permission, do not worry about a sealed system, as long as all the safety systems are in place it will make thing easier with the design of your heating system i.e. header tank feed and expansion pipes etc. you will also get away with a smaller buffer tank with a pellet or chip boiler due to the control of the boiler.

I know that you would like to to it your self, but I would recommend that you look for a Hetas registered installer as with all due respect by your own admission you do not know much about wood heating!
and this will ensure you comply with the building regs. for the future if you look to sell the house.

Terrier.
Hi, I did start out considering pellet and chip boilers but the initial costs (3x or more than a straight log boiler) put me off. Then I read about the issues of having to ensure the storage is completely dry to avoid rot and the fact that there doesn't seem to be a supplier within 30 miles led me to the current thinking of the log boiler. I guess if it all gets too much the boiler can always be substituted later for one with more convenience. As pointed out above, the store is the single most expensive part I'm considering - let alone the hassle of replacing it!
Good points on building regs. We're not planning to move for a very long time so will probably take the hit of getting it certified later if required - it'll probably change over time anyway :)
Regards,
James
Good point on building reg


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: Fiddlers on August 20, 2009, 09:04:48 PM

There really should be a 'useful theory docs' wiki page I could point you at, but you'll have to search the forum.
here are some useful threads:
http://www.navitron.org.uk/forum/index.php/topic,3411.html
http://www.navitron.org.uk/forum/index.php/topic,2281.html
http://www.navitron.org.uk/forum/index.php/topic,3857.html

Oooh, oooh, more to fill my little brain with  :laugh: thanks!


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: Fiddlers on August 20, 2009, 09:10:34 PM
"Has anybody managed to install a 1500/2000 litre accumulator (probably Akvaterm) in a garage?"

I've got a 2,500L Akvaterm (and another 2,500L plain-Jane tank alongside it) in my garage.
...snip...

If you live anywhere near Suffolk let me know - you are welcome to come for a look-see and a chat.

Threads about installation of my systems are here:

60kW Log Batch Boiler and 5,000L Thermal Store Project Report (http://www.navitron.org.uk/forum/index.php/topic,5875.0.html)
    
6 x 30 tube 58mm Panel Project Report (http://www.navitron.org.uk/forum/index.php/topic,8251.msg87452.html#msg87452)

Blimey, nice response, thanks! There's a recurring theme of using a 2nd tank for DHW in the good Solar months which makes a lot of sense. Does anyone have such a system running? I'd like to see a piccy if possible of the setup...  sadly I'm nowhere near you (Southampton currently, soon to be North Dorset). I've read your full post on the install of the system. Very nice and an inspiration to many of us I'm sure!


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: Fiddlers on August 20, 2009, 09:14:08 PM
P.S. Consider retaining your existing boiler, or a modest replacement using the same fuel, as an additional heat source to your thermal stoe.  Useful to have an automated boiler when you go away ... or perhaps to keep the house warm if you break a leg and can't cart wood ...
Sadly the only thing we currently have for heating and DHW is a fairly ugly 80's Rayburn in the kitchen. Rigging that up to the boiler/store in the garage would be more effort than it's worth I suspect. We also need the space for a new leccy cooker :)
Thankfully we do have a log burner in one room, which will be easy given we'll have several tons of logs for the boiler!

Cheers,
James


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: Brandon on August 20, 2009, 10:40:16 PM
fiddlers, i am intrigued by your comment that a pellet boiler is 3x dearer than a log batch boiler.

With a pellet boiler there is no need for a thermal store, as it is an automated boiler just as a gas or oil boiler would be (I am not going to address in this post the merits of a thermal store as a means of CH buffering), but you could simply run a pellet boiler into an S-Plan heating system for example.

By the time you have added the auxiliary controls, pumps, valves (and the installation of them) you will find that a log boiler as a complete system will be at least as dear as a pellet boiler.

I am not trying to sway you in one direction or the other, but I am alarmed at the amount of people I meet who have installed systems that were not ideal for them (usually due to a lack of decent fuel supply, or over/under sized).

Most problems we encounter with "under-performing" systems are due to wet timber (about 70% less efficient, as the water has to be boiled off).

Farmers have long since solved keeping feed dry, and that is effectively pellets, just not wood.


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: kristen on August 21, 2009, 07:30:00 AM
"There's a recurring theme of using a 2nd tank for DHW in the good Solar months which makes a lot of sense. Does anyone have such a system running? I'd like to see a piccy if possible of the setup."

I think the general idea is that the Solar heats the DHW tank first, when that is hot the "dump" circuit (its a feature of a solar controller) switches a motorised valve (or a second pump) so heat goes to the larger store.  You then need a separate "dump" circuit if the larger store could ever reach maximum - that could just be a tank-stat that turns the central heating on!

"Sadly the only thing we currently have for heating and DHW is a fairly ugly 80's Rayburn in the kitchen. Rigging that up to the boiler/store in the garage would be more effort than it's worth I suspect. We also need the space for a new leccy cooker Smiley
Thankfully we do have a log burner in one room, which will be easy given we'll have several tons of logs for the boiler!
"

I've got a pair 0f 9kW immersions on mine.  It will be blindingly expensive if I ever have to use them, but it would keep the house frost-free.  My old oil boiler broke down in the depths of Winter.  Took the "engineer" a week to fit us in. We have one open-fire, and one calor-gas mobile-stove thingie.  The house was COLD after a week. So I think the fact that a Thermal Store allows multiple heat sources means that folk should seriously considering having some sort of alternative. (Not to mention that a log boiler requires someone to be there to load it, and that can make going away "difficult")


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: Fiddlers on August 21, 2009, 08:48:13 AM
"I think the general idea is that the Solar heats the DHW tank first, when that is hot the "dump" circuit (its a feature of a solar controller) switches a motorised valve (or a second pump) so heat goes to the larger store.  You then need a separate "dump" circuit if the larger store could ever reach maximum - that could just be a tank-stat that turns the central heating on!"

Sounds simple enough for the heat supply. What I'm not so clear on is how I'd switch the DHW between the main accumulator and the small DHW tank. Or would I always draw DHW from the small tank and heat that from the accumulator when Solar isn't providing any heat?

"(Not to mention that a log boiler requires someone to be there to load it, and that can make going away "difficult")"

Good point. Not that I'll have any cash for going anyway for several years after I've purchased the house and sorted the heating  ::)
Hmmmm. Maybe the Rayburn goes to the garage too as a backup heat source.


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: dhaslam on August 21, 2009, 09:30:27 AM
My solar panels heat a 250 litre cylinder, rather than the buffer tank.    The heat dump trnsfers heat to the 850 litre buffer tank and the latter can be cooled quickly by opening the insulation.    There is a separate difference controller  for transferring heat back to the DHW cylinder.  The buffer tank is heated by a stove and sonn by a heat pump as well.


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: kristen on August 21, 2009, 02:15:31 PM
"What I'm not so clear on is how I'd switch the DHW between the main accumulator and the small DHW tank. Or would I always draw DHW from the small tank and heat that from the accumulator when Solar isn't providing any heat?"

I would suggest that there is a pre-heat DHW coil in the buffer tank, and then a primary coil in the small DHW tank.  That way if there is any heat in the buffer that is used "first"

What I'm not sure about is what happens in the winter.  No solar, no heat in the small DHW tank ... (or on those days where there is not enough solar ...). Perhaps the boiler also heats the small DHW tank as a priority, and then the buffer tank?

As a refinement I suppose you could have a mechanical valve that passes the preheated water through the small DHW tank only if the small DHW tank is hotter than the top of Buffer.

Although, if the preheated water is already at, say, 60C there is no point passing it thought the small DHW tank at all. Might as well keep the small DHW "heat" for a cloudy day, instead.

You will need a thermostatic mixing valve blending cold into the DHW to reduce it to 60C (or whatever you set) before it enters the DHW circuit (or you need thermostatic vales at point-of-use, but allowing 90C water to enter the DHW circuit is going to cause huge thermal losses in the DHW pipework, so water entering at the lowest acceptable temperature** is preferably)

** which is basically the temperature at which the furthest most tap still provides hot water at an acceptable temperature, and possibly having considered any legionaries issues.


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: Nuosmaa on November 06, 2009, 02:10:15 PM
"you might like to clarify your '10C' standing losses. Standing losses really should be in kW rather than degreesC :-)"

Indeed. (I calculate that it is about 29kWh for my 2,500L store)"

That is an enormous loss from a tank with 100 mm polyurethane insulation. Urethane with lambda less than 0,028 and surface area of approximately 12 sqm simply calculating you should be in a fraction of that if the connections are properly insulated. I attached a thermal image of a similar tank of which you can clearly see where the heatloss is coming from. I would suspect heatflow on gravity to some pipes if your figure is with no heat consumption.


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: lightfoot on November 06, 2009, 03:09:50 PM
Welcome to the forum Nuosmaa - I hope we'll be hearing more from you.



Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: Nuosmaa on November 06, 2009, 03:35:08 PM
Welcome to the forum Nuosmaa - I hope we'll be hearing more from you.

Thank you. You might be hearing more.

Continuing the previous: heatconductance is easy to calculate with insulation since the conductance will most likely be slower than the convection.
E (W)=    Lambda x A (sqm) x (tank C - ambient C)
                           insulation thickness (m)

To get that for a certain time or to get the Wh, just multiply the answer by the hours.


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: lightfoot on November 06, 2009, 04:33:31 PM
Welcome to the forum Nuosmaa - I hope we'll be hearing more from you.

Thank you. You might be hearing more.

Continuing the previous: heatconductance is easy to calculate with insulation since the conductance will most likely be slower than the convection.
E (W)=    Lambda x A (sqm) x (tank C - ambient C)
                           insulation thickness (mm)

To get that for a certain time or to get the Wh, just multiply the answer by the hours.

Hi Nuosmaa,

Unless I'm having a senior moment, I think you may of made a typo in your calculation - if the units for the K-value (Lambda) are W/mK etc, then the insulation thickness should be in m and not mm......

E (W)=    Lambda x A (sqm) x (tank C - ambient C)
                           insulation thickness (m)



Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: Nuosmaa on November 06, 2009, 04:38:51 PM

Hi Nuosmaa,

Unless I'm having a senior moment, I think you may of made a typo in your calculation - if the units for the K-value (Lambda) are W/mK etc, then the insulation thickness should be in m and not mm......

E (W)=    Lambda x A (sqm) x (tank C - ambient C)
                           insulation thickness (m)


Thanks for the correction.

Yes, not a typo, but some shortcirquit as writing the units. So now corrected so the faulty formula won't be used.


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: Fiddlers on January 30, 2010, 10:36:51 AM
Hi all, long time since I've posted but I wanted to finish this thread off in the hope it's useful to others.

I've ordered a package through Eco Angus consisting of a 25KW log boiler (Orlan Super), 2000l Akvaterm (with 2 * DHW coils and 2 * spare hatches), Laddomat 21-60, mixing valves, safety cut off, etc. This will be installed in the garage with Uponor quattro underground piping to link up the house. I'm leaving the installers to supply the pipework, Uponor, chimney, lagging, etc. I'm planning to do the donkey work like prepping the garage & digging trenches.

Even with the good insulation on the Akvaterm I'm planning to box the tank in with walls packed with as much insulation as possible, with a door for inspection.

As for prices - going the Kotly route and shopping around for the Akvaterm would have been slightly cheaper (only by a few hundred quid overall) but Eco Angus came up with a pretty good package price and since I've not installed any of this before I'm happy to pay for local support, backup, parts supply, etc.

I'm planning on posting a sequence of install pictures along the lines of Kristens mega post, only for a slightly more humble system :)
Boiler & tank should be here in the next couple of weeks. Exciting times!

James


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: ewart on February 03, 2010, 03:48:33 PM
James...i think you may have made a prudent move.
I double checked with Kotly on their guarantee. It transpires that the manufacturer only supports Kotly on the guarantee for sales of Orlan Super into the Polish market.
I checked with the export manager at Eko-Vimar and he has confirmed this in writing to me.
If Kotly sell any boilers in the UK or Ireland the guarantee is worthless as far as Eko-Vimar is concerned.
If there were any problems with the boiler they are hardly going to come over and i feel that it may be difficult to get the formal UK distributor to want to help.
The Export Manager has confirmed that the guarantee is only applicable if you have bought through the appropriate contract distributor for the country in question.
Look forward to seeing the photos.
I will be ordering my boiler in March as you have done off the UK supplier.
They gave me some discount and i do not want the worry for the price difference.
   


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: Fiddlers on February 06, 2010, 10:19:55 PM
Good to see someone else treading the same path :)
The only thing I would say is the guys at Eco Angus do seem keen to help with the Orlan boilers, even if you didn't source it through them originally. I guess it's a case that the better supported the boiler the more business will come there way in the long run.

Boiler and tank should be here soon. Really looking forward to a warm house!


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: Fiddlers on June 05, 2010, 10:14:58 PM
Ahhhh, long time no post. I've a plumbing query I hope someone can help me with!

The situation is that I have an open vented radiator network (twin 15mm pipe) dating from the 80's (probably) that I don't really fancy touching at the moment and the fancy new 25kw boiler + 2000l accumulator being installed in the garage. My current problem is what to do with expansion. As I see it there are 3 main routes I could go:

1. Keep the open vented system and install a suitably sized F&E tank in the loft of the house. But - would the accumulator vent in to this properly bearing in mind the pipework connecting the 2 systems runs about 1m underground between house and garage (11m run in total)? this has the large advantage if it would work that I can legally do it myself and I understand what I'm doing (mostly!).

2. Convert to a sealed system with a fairly large expansion tank in the garage, near the accumulator. Note the accumulator is a standard Akvaterm and only rated at 1.5bar. not so keen on this, mostly because I'd have to pay for professional help  :D
I may also run into fixing leaky radiator plumbing though I guess in the scheme of things that's not so bad

3. A mix of the two, whereby I keep an open vented radiator network and a sealed boiler+accumulator and have a heat exchanger between the two systems. this sounds way too complex!

Opinions anyone?


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: Countrypaul on June 05, 2010, 11:32:25 PM
I'm not a plumber and have not installed a TS system yet - but am planning on doing so, so have read this thread with much interest. The only advantage I can see for the unvented systems seems to be that of space (no header tank needed and only a smallish expension vessel), but has the disadvantage of apparantly needing annual inspections (is this really the case?), and needs to be fitted by an accredited plumber.  There seems to be no performance advantage from what I have read.

Seems to me the pressurised system is idealy suited to smaller installations that have gas boilers and require the absolute minimum amount of space. Where space is not so much of an issue, it appears that the vented system eliminates some of the problems (but introduces others) and allows more, how shall I put this, adventurous solutions. :hysteria

Paul


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: Fiddlers on June 06, 2010, 09:59:55 AM
Hia Paul, good to see my ramblings are useful to someone! (I have another thread running detailing the install under the 'Show us yours' area). What sort of system are you planning? log batch or pellet/chip? and capacity?
My understanding is the sealed systems should be more efficient, but you're right they have the downside of needing a professional to install. Whilst I'm happy with most of the work, sealed systems scare the **** out of me :)
(there's a video on the web somewhere of a sealed electrically heated tank that's got all the safety devices removed and the holes plugged. then buried in a field and heated. does a good rocket impression when it inevitably blows up!!)

I'm also not sure that a sealed system would be that much smaller, at least in my case. Had I had the foresight to pay a bit extra and get a 3 bar rated TS then perhaps it'd be a no brainer. But with a 1.5bar store I need a fair bit of expansion volume, whichever route I go down. I'm at the stage now of planning the copper runs, hence the question of where to put all the lovely hot water!

Cheers,
James


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: martin on June 06, 2010, 10:01:47 AM
http://www.youtube.com/v/JmJoyuUJj2Q&hl=en_GB&fs=1&


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: Countrypaul on June 06, 2010, 12:14:07 PM
James,

my plans are simpler (I hope), just ASHP, Solar Thermal and a WBS. I know the WBS with back boiler (probably a Dunsley Yorkshire) forces that part to be a vented system. I'm still at the early stage, waiting for planning before we can finalise a number of aspects and carry out some calculations as to how much heat we will require (and whether we will want a backup boiler for example). Size of the thermal store is therfore a large unknown for us at present.

I certainly don't like the idea of a pressurised system, even though in practice the temperature should not get anywhere near 100C, just the video Martin has posted shows what might happend if it all went pear shaped.


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: Solal on June 09, 2010, 11:49:06 PM
I think you'll need a heat exchanger between the two systems.
Retain the existing  plumbing in the property  as vented  and provide an extra  f&e arrangement for  log batch boiler.


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: dhaslam on June 10, 2010, 12:28:15 AM

1. Keep the open vented system and install a suitably sized F&E tank in the loft of the house. But - would the accumulator vent in to this properly bearing in mind the pipework connecting the 2 systems runs about 1m underground between house and garage (11m run in total)? this has the large advantage if it would work that I can legally do it myself and I understand what I'm doing (mostly!).


Does  it have to go underground?   


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: Fiddlers on June 10, 2010, 11:40:16 PM

1. Keep the open vented system and install a suitably sized F&E tank in the loft of the house. But - would the accumulator vent in to this properly bearing in mind the pipework connecting the 2 systems runs about 1m underground between house and garage (11m run in total)? this has the large advantage if it would work that I can legally do it myself and I understand what I'm doing (mostly!).


Does  it have to go underground?   

Yep. The garage and house are separated by a driveway - hence the trenches and Uponor underground pipework. The only other way to do it I guess would be some sort of suspended pipework running above the height of the tank but that would look "odd"

For the moment I'm going for a 2 stage approach and getting the boiler and tank connected with a f&e tank in the garage to provide DHW over the summer. Later I'll worry about how to couple up the heating.


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: Baz on June 11, 2010, 12:18:16 AM
The implication is that the expansion pipe goes up then down again under the drive. This will fill with air whose expansion on warming and response to pressure spikes as valves are operated might cause some odd effects. There are auto vents for this. A nitpicking inspector would probably not like it as initial steam bubbles on a boil up would not have a free upward escape route.


Title: Re: Biomass for DHW & Heating with solar - lots of questions!!
Post by: Fiddlers on June 11, 2010, 08:17:04 AM
The implication is that the expansion pipe goes up then down again under the drive. This will fill with air whose expansion on warming and response to pressure spikes as valves are operated might cause some odd effects. There are auto vents for this. A nitpicking inspector would probably not like it as initial steam bubbles on a boil up would not have a free upward escape route.

Yep, the implication is exactly that.... good point about air. Looks to me like I'll go with 2 systems isolated by a HE. ho hum.