Greg
Member
Hi, I'm looking for a cheaper alternative to the Latento unit(google if you have not seen them before)to store heat from Solar and probably a wet back wood heater. Has anyone come across any Australian made systems or has anyone made their own?
I want to extract hot water for showers etc and for hydronic heating. I want to ensure the systems don't intermix so heat exchangers need to be part of the solution.
thanks in advance
ghostgum
Member
I haven't seen anything, and suspect it would be custom job. For hydronic heating, I worked out that you need 1000-2000 litres of water to last from a sunny day into a cloudy day. My thought was to use a stainless steel rainwater tank, then to build the insulation around it, because I can the tank under my house and out of the weather and sun.
Have a look at what people have done on http://builditsolar.com/
What sort of hydronic heating? Floor or radiant panels?
Greg
Member
Thanks - I had a look at that site so have a few ideas but hoping not to reinvent the wheel, plus I don't want to build something and setup harmonics in the heat exchanger etc
plus need to find someone to build it. Also need to ensure thermosyphon will happen in case of power / pump failures. I don't want a steam powered rocket in the house.
I am planning on a combination of floor and radiant panels. All in the design stage.
ghostgum
Member
Mythbusters did the steam powered rocket, but they needed to remove the temperature/pressure relief valve. They used electricity to heat the tank, allowing them to easily measure the energy input.
I'd like to do a retrofit of solar boost to my radiator panel hydronic system, but current estimates are that it will be expensive given the amount of gas that I could save.
Is this a retrofit to an existing building, or a new building? If the latter, then heat storage in the bricks and concrete of the building might be cheaper.
I too am looking into this sort of a system. We are planning on using evac tubes, insulated storage and in slab hydronics. I haven't yet found an alternative to the latento and so am inclined towards custom built (or re-purposed) tanks. Steel caged IBCs might be OK though I'm not sure about their ability to withstand really hot water. The plastic might start getting a bit soft above 60 degrees I think. They are cheap and package up nicely to go under our house though. More work required here.
We are looking at in slab hydronics because of the lower water temp requirement. It might be a bit of an ask to get water up to 70 degrees to work in radiant panels whereas the 40-50 degrees used in the slab seems much more achievable.
Ghostgum - I agree that there is significant thermal mass in the building structure and this would be a useful place to store heat. The problem with this is that you can't control the dissapation of that heat into the living space. When the water is stored separately you can control its deployment with the use of a pump/controller. If the building materials are the heat store then you could only store so much before it would cause the building to overheat. At least that is my thinking at the moment. Does that sound logical?
ghostgum
Member
An acquaintance also argues for using active systems for solar heating, on the the basis that you can control where and how much heat. Although the passive camp would argue that if you do it right, you don't need to do so.
Radiant panels heat dissipation figures are based on 70C water. They still work at 40-50C, but at only a fraction of the capacity. That just means that your pump has to run a bit more. If the objective is to keep the house warm overnight, then 40-50C water may be Ok.
Greg
Member
Bit of a biased article perhaps but it sums it all up nicely. http://www.solarhome.com.au/?paged=2 "Solar Hot Water? It’s all in the tank."
I wish these guys (http://www.azureenergy.com.au/index.php)could offer me a solution at a reasonable price. I've seen H2 storage systems before, one guy in the US and in Malaysia (pretty cheap too) http://www.worldchanging.com/archives/000604.html.
I keep chasing my tail on this stuff waiting for someone to deliver. Ah well , go with what is best at the time and replace it later.
Not sure how much these are but could be an alternative
http://rotex-solar-hot-water-hydronic-heating.com.au/html/domestic/34/solar-stratified-storage-tank
I doubt the value of stratification in a tank for space heating.
- It is not like for hot water where it makes some sense to be able to 'suck' the last bit of hot water from the tank
- There is higher heat loss caused by the higher temperature differences at the hot end
- it needs more materials for heat exchangers
- in the case of Latento the heat exchanger add heat resistance to heat transfer (= reduced efficiency).
I have bought 2 500L stainless steel tanks (with two internal coil heat exchangers) from China for about 500$ each. Import and transport added about the same amount. So I got two 500L SS hot water tanks for about $1000 each. I doubt if the purchase price of a Latento tank comes even close.
I ordered these tanks from China. Low cost and good quality. Sea freight to Australia is cheap. But fees, charges and transport in Australia is expensive. Could be much cheaper when ordering container loads.
These tanks like all directly sourced solar hot water products do not have Watermark (compliance with Australian standards) but as far as I know this is not relevant if they are not connected to mains water.
Jeffbloggs
Member
s2s
Are these SS tanks pressure tested, do you have any specs?
BTW I think you are correct with the heat stratification, it only really works with low flow feeds and large capacity tanks which actually allow for the water to be largely undisturbed.
However you said:
"There is higher heat loss caused by the higher temperature differences at the hot end"
What do you mean by this? HE function best when operated at max Delta T.
argonaut
Member
There has been quite a bit of work done on stratified tanks in NZ for warm water feed in, believe it or not, the dairy industry. They have found that a simple siphon system restores the sharp cutoff band necessary for a stratified tank to work.
The Rotex tanks have been installed in quite a few hospitals around Sydney and seem to work fine coupled to evac tube panels.
mick_queensland
Member
Hi everyone,
I thought I would post a question in this thread, rather than start a new one, since it would fit here. I am planning to install a Solar HWS in the very near future. I am still getting quotes. During my research into SHWS I found there are two main stainless steel hot water storage tank manufacturers in Australia. Does anyone know or can point to a link that tells which stainless steel tank has the best performance and insulation? I feel very certain that the performance of the whole system relies on the tank to keep the water hot for several days (poor Sun days)
Cheers, Mick
Skysolarman
Member
good luck Mick , this website shows all tanks that are certified in Australia http://www.energyrating.gov.au/
mick_queensland
Member
Thanks for that Skysolarman, that is a reasonably useful and totally unbiased review. Exactly what I was hoping for.
Its a link worth clicking on if you havent already checked it out.
Cheers again
Mick
