Drilling has begun

The ground source heat pump is going to extract low grade heat from the ground, and concentrate this into high grade heat in the form of hot water for taps, then under floor heating then the hot tub.

There will be 3 bore holes down which liquid is pumped to be warmed by the heat of the ground, up to a bit short of 100m down !

Lowering & driving the drilling rig down the rear stairs:

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The drilling head:

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Drilling, with all the dust, which was a lot more than I expected.

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Dust on the solar panels that are going to need a clean (or for it to rain so they self clean, apparently).

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A growing pile of dust by the drilling rig. This later turned to slurry as the drill got to a depth where there was ground water. 2014-05-15 09.06.20 (2)


Thermodynamic panel :: A happy user

One of the long GreenBuildingForum threads on Thermodynamic Panels has had some comments from somebody that installed one on their property in Northern Ireland, 18 months ago:

  • “I have had a thermodynamic panel installed for 18 months now and so far I can’t find fault with it.”
  • “It provides all the hot water requirements that is asked if it.”
  • “I have never switched on the built in immersion even when it has been -10 degrees outside and the panel has had an inch of ice on it.”
  • “I couldn’t justify solar as lets face it who wants something that only works well 7-8 months out of 12 then you need an additional piece of kit as back up, or pay £3000 per bole hole for a ground source heat pump when you don’t have enough land for slinkies or have their own personnel forest to supply a log boiler.”

Installed System

  • £4,100
  • Panel
  • 280 litre cylinder
  • pump and fittings
  • County Down, Northern Ireland
  • “Currently there are 4 showers every morning, plumbed to dishwasher and washing machine, and and usual washing in the sink when items don’t fit in the dishwasher.”

Green Roof & PV

From the Winter 2012 copy of Green Building Magazine (volume 22, No3).

Two green roof studies. One, carried out in Berlin, where green roofs had been installed in the 1980’s. They varied the PV arrays to find the most efficient:

  • Over 5 years, PV panels over a green roof Vs a bitumen roof has 6% higher yields.
  • If over a green roof AND on a swivelling stand that tracks the sun, then 10% higher.

So green roofs boost PV productivity AND as they insulate the roof, they decrease the amount of energy needed for heating and cooling.


The second study looked at planting schemes. The most popular current choice is sedum, du to high resistance to draught. Sedum was compared to Stachys byzantian, Hedera hibernica and Bergenia corifolia.

Stachys byzantina (commonly known as Lamb’s Ear) outperformed the other species in terms of leaf surface cooling, cooling the substrate beneath it’s canopy and even the air above it’s canopy during short intervals over hottest periods, when soil moisture was not limited.

The conclusion was to not choose the best plants for a shallow substrate, but those that provide the best all round environmental performance, including bio diversity. This may involve deeper substrates and some form of irrigation.

Hot water heat recovery via the Thermal Store?

Instead of, or in addition to a heat squirrelhow about sending the domestic hot water (DHW) waste via a coil in the thermal store?

It should be easy to have a thermostat that checks if hot water being “thrown away” is above the temperature of the lower section of the thermal store, and if so, sends the water through a heating coil in the thermal store, so it passes over some of it’s heat before it goes down the drain.

From www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8005

  • water leaving the shower head at 42 deg C will have cooled to around 37 deg C by the time it gets to the drain.
  • The 5 deg heat loss will already have been recovered to the house (assuming effective MVHR on the shower room exhaust).
  • The heat squirrel holds 120 litres of hot waste water, to pre-heat any incoming cold water that is heading to the heat store.
  • By holding the hot water, there is more time for the heat transfer to any incoming cold water, especially any that sits in the coil inside the heat squirrel.
  • Hopefully this 120 litres of water is regularly self flushing as “grey water very quickly turns manky when stored, even for short periods.”

Hot Tub Hot Water Heat Recovery

One key thing here, is my plan to have a log fired hot tub.

  • I’m looking at hot tubs that use logs to get the water up to temp and then keep the temp there.
  • BUT to accelerate getting it up to temp after it has been left a while, I want the option to top it up with hot water from the domestic hot water supply.
    • Reading elsewhere, hot tubs tend to run around 36° degrees.  Although friends with hot tubs say they tend to run theirs between 37° degrees and 39° degrees.
  • I also want the option of taking water from the hot tub, when it’s not going to be used for a while and sending this via a heat recovery option back to the heat store.
    • I accept that sending “lumps” of less than 120 litres at a time will optimise this in terms of giving the water time to transfer it’s heat to the heat store / cold water coming in to the house.

Thermal Store

This is part grabbing historical Thermal Store notes to one page, and part adding new notes.

Click here for notes on Thermal storage – pros & cons.

Looking at the Akvaterm thermal stores (which can go up to 5,000 litres !!)

From www.stovesonline.co.uk/wood_burning_stoves/Akvaterm-Geo-Thermal-Stores.html:

  • have a stratification baffle plate about a third of the way down the tank. (see photo below). This can be optionally upgraded to an insulated baffle to further improve performance but the added benefit is not huge as it is very good already.
  • Once the water above the baffle has been heated to a high temperature by the heat pump (50ºC-60ºC) it then shifts to heating the bottom two thirds of the tank to a much lower temperature suitable for underfloor heating (around 40ºC).
  • OR if / when the heat pump is generating lower temp water (often more efficient COP) it only targets the bottom section.
  • larger than normal lower domestic hot water coil. This is to ensure that the incoming mains water picks up as much heat from the bottom of the tank which holds the ‘cheaper’ heat produced at a high C.O.P.

From www.ecoangus.co.uk/Akvaterm_Solar_Plus_Accumulator_Tanks.html:

The AKVAir Solar Plus is available from 300-2000 litres and is 3 bar pressure rated. The tank has 4 coils, two for solar input and two for domestic hot water (DHW) and is divided by a baffle plate, approximately 60% below and 40% above the baffle. Each section contains one solar and one DHW coil and all coils are positioned vertically.

The AKVAir Solar is available from 300-2000 litres and is 3 bar pressure rated. The tank has 3 coils, one for solar input and two for domestic hot water (DHW).

From www.accumulatortanks.co.uk/Solarplus.htm:

Akva Solar plus coils diagram   Akva Solar diagram key

Akva Solar Plus coils + baffle plate     Akva Solar Plus coils


From www.akvaterm.fi/eng/Accumulators/AKVA_SOLAR.41.html:



From www.akvaterm.fi/eng/Accumulators/AKVA_GEO.206.html:

  • AKVA GEO is suited to all heat sources (others seem to be solar or something specific).
  • example layout:



From www.navitron.org.uk/forum/index.php?topic=14183.0:

Heating System Schematic

Dual Cylinders?

From www.chelmerheating.co.uk/dual_cylinder_thermal_store_systems.html:

  • For larger domestic and commercial projects, our dedicated heating buffer cylinders are used in conjunction with our high-gain unvented cylinders to allow greater variation between heating and hot water demand.
  • The separate low-temperature heating buffer allows the small, infrequent heating demands of a property that is “up to temperature” to be met by stored renewable energy before activating the heat pump/boiler to reduce wasteful on/off cycling.

An alternative Hot Tub

I’ve thus far been considering a Dutch Tub hot tub:

  • I think they look cool
  • Their water volume is “only” about 650 litres, so not too much to heat up and keep walm. Also not too much weight.

BUT their size does mean while they are super comfy for 2 people, as soon as you go over that, it gets a bit of a squeeze. (the bottom of the Dutch Tub tubs domes up).
Look at these 2 pic’s of 1 and 2 people in a Dutch Tub (there is only one size). Click on either pic and you’ll get the full size version where yu can see toes at the other side of the tub and arm spans etc.

dutchtub-2_people    dutchtub-1_person

I’ve just found Cashen Hot Tubs. Their tubs are 100% made from timber from local (Cornish) forests. Mostly from Dutchy controlled forests less than 6 miles from their sawmill.

They come with a wood burner heating option that looks the same as the hot tubs I was in at last years (2012) Nova Festival:

Wood fuelled hot tub at Nova Festival 2012


The 1.7m diameter Cashen hot tub is down as suitable for 4-5 people. It’s about 400 kg empty, so add the 1,800 litres of water, the burning fire and a few people and you rapidly get to 2,500 kg or a bit more.

  • The inside depth of the tub is 920mm, outside height is 1090mm. They have said they can make a shallower tub to make the most of your sea view. But will that mean cold shoulders ?
  • They can also add a filtration system to the wood fired hot tubs.

Below are some photos and other info from the  Cashen Hot Tub Website and some emails from them (so accurate early 2013):

Wood Burner Hot Tubs (Elec heated a bit more £)
1.5m (4.5ft) dia. 1,600 litres seats 3-4 people £3,125
1.7m (5ft) dia. 1,800 litres seats 4-5 people £3,475
1.9m (6ft) dia. 2,500 litres seats 5-6 people £3,725

The tubs have an “inside depth of the tub is 920 mm, outside height is 1090 mm. If you were interested in a shallower tub to make the most of your sea view, this could be accommodated.”

Prices include our eco-friendly underwater wood-burning heater and integral seating as standard.

The stove is made from marine grade aluminium. They can be replaced at £800.

Hot Tub Optional Extras
Wooden Steps (I assume external to get in and out !) £195
Lift off wooden cover £265
Lift off custom made insulated cover £350
Pipe work screening
– which it looks like the Nova Festival tubs had. The Cashen photos below show tubs without a cover over the pipe work.
Filtration system £515
Stainless steel finish for chimney £180

Water Temp & Stove Size

Reading elsewhere, hot tubs tend to run around 36° degrees. The stove needs to be sized to not over or under heat the size of the tub.

Hot Tub Placement & Maintenance

The more they are not left the better.

“Use it and wash it regularly, another important thing is to make sure the is adequate air circulation underneath the tub. There is no problems using sea water in the tub as the stove is a manufactured of marine aluminium, the actual barrel itself works better with salt water as it keeps the moisture better and it slows down the dry out process.”

Photos from the Cashen Hot Tub Website:









From another Website:

wood fired hot tub - schematic

Hot water heat recovery

What device(s) to put where to recapture as much of the heat from waste / grey water needs a decision.

The solutions from www.recoupenergysolutions.co.uk are clearly all very efficient and appear to be the same or similar to those that are well used in the US, where a lot of properties have their heating systems in the basement.

They are based on an “instant” transfer of the waste water heat to the mixer in the shower and also to the cold water feed to the water heating system.

BUT, the planned house will have clothes washing machines, a dishwasher and 2 showers on the ground floor. Being on the ground floor they wouldn’t work with all the recoupenergy solutions. Also a washing machine, dishwasher, bath (or hot tub) generates the waste water, some time after the hot water tank has been re-filled with mains cold water.

So in those circumstances, the www.esavep.com/products/hot-water-cylinders Heat Squirrel (scroll to the bottom) could be better and could provide a single (so a lot cheaper) whole house solution for all waste / grey hot water heat recovery. They are about £399 (not installed). The heat squirrel has a 120 litre capacity.

A key consideration / idea will be:

Can the waste water input be regulated so that only waste water that is warmer than the water in the heat squirrel is let in to it?

It seems that for a shower, the recoupenergy solutions will be the most efficient, but for the whole house, and the total cost, a single heat squirrel could be better than a heat squirrel and one or more recoupenergy solutions.

Heat Squirrel Schematic

Heat Squirrel - schematic
Heat Squirrel - installed

Cold water tap temperature

I was pondering the temperature of the cold water tap!

To get hot water, a domestic hot water system needs to take the cold water up to around 50 degrees C.
– I know there are also considerations to periodically take it above 60 degrees C to prevent the Legionella bacterium growing in the water system.

Looking at the chart below from  http://www.zenexenergy.co.uk/Zenex1/index.php?option=com_content&view=article&id=9&Itemid=5&limitstart=1:


Seasonal variations in domestic hot water energy requirements


I assumed that the mains water pipes were deep enough to cause less seasonal variation in the output temperatures, between 4°C in the winter and up to 20°C in the summer.

I’m not sure why the graph has a lower summer temperature for domestic hot water (DHW).


Exhaust air into a hot water heat pump ?

I’ve been sent some info by Cernunnos Homes (“Renewable Energy specialists for the domestic & commercial sector.”) in praise of the  ESP Ecocent system. Peter one of the Cernunnos founders has put this into his own house:

If you not decided on a hot water system – take a look at the ESP Ecocent.

No RHI (exhaust air source is not considered green)

Can be integrated with RegaVent MVHR system (so in the summer the Ecocent can cool the house by recycling the air from which heat extracted back through the ventilation system).

When I got back to them about this meaning that the MVHR system isn’t re-directing captured warmth from air being expelled from the house to the cold air being pulled back into the house, they replied:

“…. normal MVHR is transfering heat out to  heat in.
However in the summer you want heat out and cold in, which is what the Ecocent delivers by cooling the air via the compressor.
In the winter we can either bypass (so extract and expel from the outside and leave the MVHR as a traditional system) however normally people either shower in the morning (before they go out to work), or in the evening (before they go out to socialise) or at end of night (when you want to let the temperature fall in the house). At these points (when the bathroom is over heated) the MVHR then kicks more heat back into the house when one would naturally be comfortable with it not recovering the heat to recycle to space heating, but there is a demand for water heating. So whilst either use (space or water) for the outgoing heat is an efficient use of that heat it can be argued that the water heating (with very low heat loss) is a slightly more efficient use of that heat! It is energy efficiency at the extremes, ie being efficient in the most efficient manner possible!