Following some of the comments on my coal discussion thread, I've been looking at alternative ways to change to a renewable energy source. I've given up with wood pellets, getting the 'stove' type appliances is just too difficult (and therefore risky for support and maintenance) and have found a nice source of wood that I intend to use on my multifuel stove - though I may keep a little some coal going

So in a wave of new thinking, I've looked at alternatives and would like to consider using three heat sources for my hot water and central heating (using a thermal store)... the multifuel stove for heat top-up; solar panels vertically mounted on a south facing wall for spring/autumn heating boost; and a ground source heat pump. I've found some nice solar panels that could do the job though I'm tempted to have a go myself and make something. I can also connect up the multifuel stove using temperature sensors and a pump (i.e. change from gravity feed to powered feed).

I've UFH downstairs and rad's upstairs, so it's a great combination that I intend to use as 'ufh heating on three seasons' and 'radiators on when very cold'.

The thing I'm having a problem with is two fold..

1. None of the heat pump resellers/manufacturers that I've spoken to recommend a thermal store (except Worcester, but their output and price is just too excessive for me). I like the technology by the manufacturer based in Cornwall (and the local production), but they actively discourage the use of thermal stores on their site, but don't give any real details of why. I'm only looking at a bottom of the range 1kw input heat pump that can run off-peak. Is there a real reason why I can't use heat pump's with thermal stores?

2. None of the major thermal store manufacturers offer options for three 'input' heat sources. Do I just run the heat pump and multifuel stove off the heating ring? Anyone have any recommendations?

Chelmer Heating do a thermal store and you can specify additional input coils

http://www.chelmerheating.co.uk

Interesting options list Adrian!

The reason many manufacturers don't recommend thermal stores is not because they don't work. In several ways, a thermal store demonstrates best practice and allows best use of a heat-pump's characteristics - fewest stop-starts for example. Smaller heat pump possible due to buffer. Cheaper running costs on E7. Ability to add different fuels, now or in the future.

Rather, it seems to me after much discussion with mfrs that their lack of interest in thermal stores is self-serving. They have 'A' solution they want to sell you, which is unique to others, cheaper, so gives them commercial advantage. A thermal store, (while the Best Available Technology - BAT) is large, expensive and likely they would lose the sale if they tried to sell it to most people. Using a heat-pump with economy 7 allows cheapest possible use of the pump - and if you can store the heat from this period, that saving must be weighed against rising fuel costs and the initial extra cost of the pump. Against this again is the reduction in cost which your woodburner/solar would bring to the equation. Me? 1000 litre thermal store, woodstove and HO boiler, heat pump and solar...eventually

Regards, Crusoe.

or just ditch the heat pump and use your solar optimised for the summer and the burner for the winter and the two combined for spring & autumn

Posted By: tom.harriganI don't see the point of a thermal store. Why store heat in an expensive tank, when you are extracting it from stored heat in the ground?

Also, many thermal store manufacturers specify an upper store temperature of around 80c if you want hot water. That is just ridiculous if you are heating it with a gshp. (It knocks boilers out of condensing mode too!)

How about running your heat pump in the most efficient way, and just doing your under floor heating with it? Then you can use you higher temperature heat sources to do a mains pressure hot water cylinder and upstairs radiators.

What you say is fine if enough heat is readily available under the ground and the heat pump is man enough to extracts it in usable temperatures, then no storage is needed. However that is invariably not the case, so storage is needed. Because of low temperatures extracted by heat pumps, low temperature UFH is generally the best heating system to mate with the heat pump. The highest temperatures gained from heat pumps tend to extract heat from moving water.

The reason for thermal storage is:

1. To store heat to use at peak times. The heat can be gained overnight using cheap off-peak electricity tariffs.

2. The important buffer effect that reduces or eliminates boiler/heat pump cycling.

3. It is a wonderful neutral point. Many heat sources and heating systems can use the neutral point and each one operates quite independently and does not effect the other. Divide and rule.

A decent thermal store, or rather heat bank, (a heat bank is a store using a plate heat exchanger for DHW take-off), can run at at 60C and give DHW at 55C - stratification helps a lot here. Those that run at 80C tend to be internal coil DHW take-off units. The efficiency of the plate heat exchanger to the internal coil is night and day. Thermal stores running at 80C do not knock condensing boilers out of condensing operation. On re-heat a condensing boiler will be condensing 80% of the reheat time on a store with a 80C setpoint.

A well designed heat bank using spreaders and a RAVK valve on the DHW plate heat exchanger, or a modulating pump, can have 70-75C at the top and 20-25C at the bottom of the cylinder. When the boiler kicks in, high efficient condensing operation is guaranteed - even in summer. The lower the return temperatures the more efficient.

By inserting a blending valve on the boilers return a non-condensing boiler's efficiency can be enhanced. Set to just above dew-point (no condensing), about 58-60C, "peak" efficiency is then obtained for most of the boiler's reheat. Peak efficiency is higher than the sedbuk 80% or so.

I have been looking at ground source heat pumps etc for my hoped for new build and having taken early retirement I can dedicate plenty of time surfing (hence I'm logged into this forum). I have read so many conflicting reports and so much marketing blurb from various companies I was doubting the viabilty of GSHP.

However I have contacted a couple of British home owners who hav e installed heat pumps and they are both very happy and it works with minimal or acceptable electricity costs, I had also considered a heat store until I learnt the cost of over £5,000! No way, I accept I may not recover my investment in a GSHP but an extra £5000

I visited an Austrian friend at his new self build during a balmy -15C last week to physiaclly check out his GSHP. The house was a warm 22C with under floor and in parts wall piped heating! Loads of glass and high ceilings in two years he has needed his 3KW immersion heater for 6 hours which I suspect may be to boost his conventional domestic hot water tank beyond 65C to kill bacteria. His 7KW immersion heater remains un-used AND HE HEATS HIS SWIMMING POOL.

I'm certainly no expert but when I build I'm sticking with a conventional DHW tank.

First posting, so please go easy on me!

Long time reader of this forum and I have learned so much as I am getting my mind around a major refurb of a 25 year old 5 bedroom, 3 bathroom, terraced townhouse which is incredibly badly provided for in terms of insulation, draughproofing, heating equipment etc.

Have read with great interest on "heatbanks" and have found the DPS website very enlightening, but can someone give me an idea of the cost of buying and installing a sizeable GXV heatbank (I have taken the view size required is circa 300 litres, but please correct me if I am wrong - storage space is not a limiting factor in size of tank). i would be running the system off a gas boiler (to be specified and installed at the same time) and considering adding solar.

Many thanks

.

Posted By: aclarkyEvening all, is anyone still here? almost 10 years on I have a similar query which I would really value any opinions on.

Convention is to start a new thread ... I'd suggest you move your post (i.e. start a new topic and repost)

EPC report says in needs 60000 kwh heating a year.

EPCs are notoriously unreliable, so get a better model if you're dependent on the answer. How big is the property?

could I pour 2m3 (5 tonnes) of concrete (equal to 1000L water), insulate it well and run a coil through it and warm it at night.

Yep, that would work. You need to account for the relative slowness of heat transmission and allow for future maintenance needs somehow. Plus the screams from eco-concious people about cement and latterly sand.

or is there another way.

The traditional answer at this point is insulate, insulate, insulate. i.e. first reduce the heat demand, then optimise the means of heating.

I am going to insulate under the suspended floor (and walls and roof as well as possible). Would under floor heating at GSHP temperatures work - the idea was to attach pipes to underside of floor boards and insulate and close off the joists.

Good, you mention insulation. I'm sure there are details that would need working out, but in principle, yes.

There is a lot of cornicing etc that would not be feasible to remove

Is the lack of feasibility due to legal constraints, or economic ones?

Hi thanks for that - as suggested I will start a new thread..