Thursday, October 29, 2009

Circuit diagram, with battery

Oct 29 : I am venturing to put this diagram on the Blog, although its not finalised. I have to discuss it with friends and experts.
As we don't know if the thermal battery will work, this is a dual system - either 2 circuits using the battery, or one circuit, bypassing the battery. It has to be manually changed with 4 lever-ball valves next to the battery.
     It been suggested that I could clean it up by using a 3-way battery (although have already bought the ball valves). However if the 3-way valve can be activated by an electric switch, that would be good.
There are Flowmeters to record all the volumes of liquid in circuits. All the pipes are 28mm, being laid to fall, with airlock release valves wherever needed.
The warmed glycol never goes to the heatpump first - it would shut down if getting glycol hotter than somewhere in the 20s. So glycol from the battery or the solar panels has to go to the ground first.

Wednesday, October 28, 2009

More Pipes, and Sasie discussion

Weds 28 Oct: installed more pipes in the loft and also worked on the drawings for the circuit and the design of the copper piping for the heat transfer elements in the thermal battery. The copper pipes are being laid dry (unsoldered), for which I am glad, as I am making a few amendments as I go.
    Had an interesting afternoon with Architect Mike Siebert, PhD student Nina Hormazabal (Nott'm Uni) and Engineer Mo Kelly (of Sasie, a company covering most of the renewable technologies, including Solar PV, Solar thermal and GS Heatpumps). Mo is interested in the wider applicability of our project. He has worked with reverse cycle heatpumps, putting heat down below to cool the building. He has looked and projects like the idea of 'renting roofs' for shared PV projects. Mike showed a website of ICAX (a company whose link is in the links section of Blog).
   Mo was interested in our thermal battery idea and the use of the low grade solar panels (good because they avoid overheating the battery or heatpump). The circuit is designed so that all heat goes to the ground BEFORE it goes to the heatpump - this is necessary because the heatpump's self protection would shut down if it received over-warm glycol directly.

Tuesday, October 27, 2009

Thermal battery update

27 Oct 2009: I think the balls I have contain Phase Change Salts, not Wax. That's not a problem as their thermal retention can be even better than paraffin wax. See the Wikipedia on Phase Change (PCM). Having discussed with BASF experts, it seems that good old WATER is still the best medium for conveying heat from the copper element to the PCM balls. There's plenty of it, we have rainwater butts full of it.
   It may need some antifreeze for the winter, but BASF have a product called Glythermin P44 which can be mixed in solution with water, and is a non toxic antifreeze, and supports heat transfer to the balls. I am more worried about a heat build up in the summer causing the water to evaporate. I shall have to check the water level regularly, and could fit a Ballcock to the tank to trickle water in, that would keep it topped up. (see interesting discussion, US patents). It will be covered and insulated, and the balls will cool the water, and some of the evaporation will condense on the lid and fall back.
    I have purchased some ball valves, so that the piping can be dual use - allowing the solar panels to charge the earth direct (as previously intended) and by changing the valves, to allow the solar panels to charge the battery, and the heatpump to draw heat from the same battery, with a different circuit.
My earlier advice to myself was to keep things simple and not introduce so many variables that proper data analysis becomes too difficult - so I ought to take that advice. Therefore, I could work with the same 4 panels as originally intended, and have the ability to switch the battery in or out just by moving the lever-ball valves.
Illustration from Colin of BASF. He writes:
"Below is a table of typical values for specific heat capacity, thermal
conductivity and freezing point for various fluids at 20 deg C. Some are more accurate than others. Water, ethylene glycol, propylene glycol are defined liquids so the values are pretty accurate. Mineral oil and vegetable oil are generic terms, and for example the specific heat capacity of linseed oil is 1.84, olive oil is 1.97. You could expect bigger variations between the many grades of mineral oil, paraffin has a specific heat capacity of 2.13, the mineral oil in the table at 1.67 is probably a typical lubricating oil fraction. The Glythermin figures are from BASF data, the glycerol data are extrapolated from published values. What can clearly be seen is the higher the water content the higher the specific heat capacity and thermal conductivity."

Sunday, October 25, 2009

Thermal Battery dilemma

25 Oct : I feel I can't turn down the use of the PCM balls for a Thermal Battery, it is too good luck to ignore. I have 480 balls, each 7.5cm diam., and these will fill a 250 litre tank perfectly, with room for two copper piping assemblies as the heating element. I can get the tank into the loft if I take out the ladder and lift it somehow, then restore the ladder.

But its problem is that it complicates things.

My original idea was beautifully simple, the low grade solar-air panels to send heat deep into the ground - the delta-T (temp difference) would work perfectly  because the ground is always cold, and the circuit could be a single large circuit. Easy. However, the idea is principally useful to people who have deep boreholes, ie. very very few. And it's fair to accept that some or much of the heat will drain away, as all my doubting friends say.

The thermal battery idea is very good (although it's a different idea) and could be applied to hundreds of houses, perhaps many more in 5 yrs time. So it's worth researching, and worth prototyping.
However, it needs a high temperature delivery, eg perhaps a pro quality flat-plate solar-thermal panel, so that there is a clear delta-T between panels and battery. The swimming pool panels would only be significantly hotter than the battery in summer and when the sun shines.

It also requires to redesign the circuit into two looped circuits with the battery as the hub (each circuit with their own pump), and thus prevent the heat-pump simply moving heat from the battery to the outside air. Using ball valves, I can change the circuit so that the battery is either connected, or the circuit is a single one as per my original plan. (I have designed something, but need to draw it an put it on the blog - also need to discuss it with the dissertation students.) I cannot depart too far from the original idea as I would leave them with a topic different from the one they started with.

I could just make my life easier and keep the 4 panels as proposed (and some of the piping is in. However, its worth considering David Atkins' earlier idea and have a mixture - two of the Swimming pool panels, and a single 2 sqm Flatplate solar-thermal panel.

For the thermal battery, I will use Rainwater as the sharing medium for the balls in the thermal battery, although BASF are interested in helping with a Micronal emulsion, and I also know that cooking oil would not evaporate - but it might get smelly. Water is easier to dispose of if that is necessary, and is adequate for proving the concept, and is free, and therefore more inspiring and possible to others as an idea to emulate.
I would test the amount of evaporation weekly in the summer and know if water is unsuitable.

Saturday, October 24, 2009

Water Tank for the Balls

24 Oct : Now that I have the PCM Balls - two dustbins and a small crate load, I have to think of how to use them. Having first thought of making an insulated plywood crate, then it was suggested to me to consider a 200 litre rainwater butt. But it would be hard to put the copper coil in through the top opening. So I have moved onto the idea of a Cold water tank, which will fit through the loft hatch. 50 gallons (240 litres 1090 x 610 x 500mm) will be enough for almost all of the balls - and being long, would be easier to make the copper piping for.
     I met a group today in the Marmont cafe who are from BASF, and they suggested that I can get liquid phase change wax emulsion  to pour in around the balls. My first idea had been to put sand in, but dry sand isn't conductive enough. Wet sand is better, but I thought it would dry out, be too affected by the temperature change and be too heavy. I am presently thinking of catering packs of cooking oil (eg Rapeseed) to bind the sand and avoid evaporating. The Micronal phase change liquid wax would undoubtedly be best, if it doesnt cost a huge amount.... either on its own, or mixed with coarse sand. Hmmmm.... think on, DNC!

Sept 2010: Update: This tank was returned to Screwfix after I decided not to use the tank or the balls.

Thursday, October 22, 2009

Plumbing and Phase Change Balls

Oct 21: I spent part of the morning laying pipes in the attic - 28mm copper pipes. I did much of the cutting to length and positioning, so they can be soldered another day.
Now that the panel positions are finalised (with flexibility provided by using rubber hose) I can now finalise the indoor plumbing and the location of 5 holes in the wall.
     Later, at the university, I was walking past a skip in our department and the technicians were wondering how to dispose of a large number of balls. They aren't allowed to put the balls in the skip as they are unsuitable for landfill. I offered to take ALL the balls as the balls are actually spheres of Phase Change Material, ie a special formulation of Salts or Wax that is suitable for use in buildings. They were left over from some lab research in 2008 into phase change materials.

 I had been wanting to have a thermal buffer in the attic to include in our experiment, but a water tank would be extremely inefficient and over bulky. A crate of PCM balls would be vastly better as their melting point is high, and they dont freeze. So the Heatpump can GET heat from the balls (which are at about 23ºC) and at other times the Solar panels can PUT heat into the balls (which remain at 23ºC). The balls will never heat to melting point because the panels are low temperature, and surplus heat will go down to the boreholes. They cant freeze as they are already solid. And I can get them through the loft hatch!
There are three dustbin sized containers of them, probably enough to fill a large wheelie bin. So a custom cubic container will have to be filled with the balls and ultrafine sand around them, with a zig zag of copper or plastic pipes going through them. This loop could be set with valves and thermo-couples to the input and output, so the performance can be measured, and the cube can be isolated if we need to do maintenance on it.

Wednesday, October 21, 2009

Immersion Heater kicks in!

20 Oct 2009: It brought home to me how valuable this exercise could be today. The Heatpump's Immersion heater function came on in the morning - the outside temperature was about 9º and inside 19.7º (so not really a lot to do), but it chose to accelerate the process with some one-to one heating - because the underfloor heating is so slow to make a real change. I noticed because the OWL meter suddenly said the house was using over 4 kilowatts! The meter reading at the end of the day was  22 kWh for the day, the highest I have seen since I started recording. (It coincided with a very overcast day and almost no PV generation).
    If Solar Geocharging can reduce this consumption - this switch from a CoP of 3 to no CoP at all - then it will be worth doing. (I had better go up to the loft and get on with laying pipes!)
If I am advising a client about a heatpump again, I would say that Underfloor heating is still best overall, but in rooms with a carpet, and in the location of the thermostat, there should be a modest sized low temperature radiator or hollow skirting - for the first to speed up the warming process, and for the second, to allow the user to tweak the valve so you can 'fool' the thermostat effectively. Our thermostat is in the hall, and if someone comes in the front door, it activated the heatpump far too quickly. is the site for our daily metering.

Tuesday, October 20, 2009

'Planning' the FOUR design

Oct 19: I had a meeting with two of the dissertation students Robert-H and Joel-C, and one of my colleagues, Dr Rabah-B, who is a supervisor.  I also had an email from David of Ice Energy commenting on the layout below.
His comment was that we would be better to keep it simple by having them upright back to the wall not projecting out on a complicated metal frame. This will be cheaper and look better.
   He also asked if we have planning permission, and the answer is that we do. About 2 yrs ago, we had the idea of fixing a wind turbine on the south wall - and Rushcliffe refused (on spurious grounds, but I am now glad that they did) and offered by way of compensation to let me have a bunch of solar panels on the south wall.  So having paid about £170 for the planning application, I agreed rather than let it be wasted, never imagining that this permission would actually be used.
   He also suggested that we might consider 2 of the solar collectors and one Flatplate Solar panel in place of the other two, to catch more heat when the sun really shines. We could not do this as it would be too confusing for the students and for me to model the combination of two types of panel, as well as the fluctuating benefits from the PV roof. In an experiment, you try to shut out unpredictables or external variables so that the data from the experiment is credible and repeatable.
   One of the long term ideas is that this idea can be packed up as an commercial add-on to a heat-pump installation, so it needs to be proven.

Sunday, October 18, 2009

Timescale thoughts - December!

18 Oct : I am keen to get on with this project, but also have realised that there is a benefit to doing meter and temperature readings without the benefit of Solar Geocharging as we move into the winter. Ideally we should wait an entire winter, so it can commence the charging during the summer, and compare with next winter.
However, this would not be a help for our 'one-year' research students who would like to see the diurnial benefits in April/May 2010. It would mean another winter of higher fuel bills (and more carbon emission as we use more coal burnt power). So I will work in a relaxed kind of way on this, until at least the solstice... so there is time for real thought on the plumbing and installation details. As there is little sun in December and January, we won't expect great things of this until the sun shines more in February and March.

New arrangement - FOUR panels across

18 Oct : I had a visitor from Mike Siebert, an architect friend who has built a few houses, and we discussed the best layout of panels. There are five things I want to do:

• One is to find a way to increase the number of panels so that the geocharging effect is measurable. Two would not be enough, in the judgement of people I have talked to.

• Two is to keep the plumbing in the loft simple and accessible and free from airlocks.

• Three is to find a way to tilt the panels to increase their harvesting in Summer - perhaps 15º.

• Four, to keep them high enough to be free of interference from trespassers and shading from the nearby tree.

• Five, to ensure a good glycol flow through the panels, avoiding the build up of 'dead spots'.

My previous layouts were somewhat constricted by my desire for access by ladder. If I am prepared to pay for the scaffolding to put the panels higher, it seems very clear that the best arrangement would be high above the south windows, where there is space to have FOUR panels across, and I am able to get a good flow, and get the pipes plumbed easily. The 15º tilt will give some solar shading to the upper windows at the height of summer.

In case anybody doubts my sanity on this experiment, I am getting clear indications that the temperature of the soil below the house is cooling as the heatpump draws more as we move to winter. Temperatures are affected by the fact that the upper 5m of soil varies, but the trend can be observed. While I was getting soil temperatures of 12.8 in summer, I am now getting 10.7, a 2 degree C drop.

Thursday, October 15, 2009

Struggling with Panel arrangements

I have started putting pipes in the loft, but stopped for a good think.

  • The Top Left is what I have near enough agreed with Ice Energy , two verticals, horizontally arranged.
  • Bottom left is more economical in piping and fits better between the window and the corner, and needs a longer piece of 40mill pipe, and needs a curvy hose or two elbows to connect the panels.
  • Top Right is an Extension of that, with the panels still vertical, but with three, as one of my colleagues thought that 2 such panels as we have will not make enough impact. I would need a third panel and more piping.
  • The Bottom Right is interesting - it's the best fit on the wall and uses the least amount of joints and piping. However, I guess the panels are designed to be used upright, and may not work well on their sides. Putting them on the side like this puts the widest parts of the panel vertical. My colleague thinks the glycol will find too quick a path through the panels, and leave dead spots at the opposing diagonal corners.... or is it possible that things will even out, and if the opposing corners warm up more, they will mix faster? would a slower or faster pump speed make a difference here. does maximum efficiency matter when we are simply dumping the heat, not trying to nudge up the temperature of water?
If you click on the illustration, it will enlarge.

Wednesday, October 14, 2009

Welcome to three students!

14 Oct : I have been discussing the project with colleagues in the Dept of Built Environment, and it is likely we will have 2, perhaps 3 students to study the project and make use of the data I have been recording.
1. We hope to have a BA student, looking at the project non-mathematically, mainly as a case study in the light of the new feed in tariff scheme, policies and economic arguments for renewable technologies, code for sustainable homes targets, etc.
2. We also hope to have an MEng student taking a more mathematical modelling approach, comparing computer models with actual data. As the BA and MEng are only working on it till May 2010, they cannot look at interseasonal thermal storage, but will be able to monitor Diurnial thermal storage, i.e. in the March-April equinox period we hope that daytime warmth will return in the cold evenings.
3. We also hope to have a PhD student, who will have a 3 year term of work on this. Although the first year is often spent on literature research, the data will continue to be collected, and the total of three years will reveal the full effect of three summers and winters alternating to see if there really can be interseasonal storage that makes an economic benefit (as well as recording the diurnial benefits.)

It is a complicated equation trying to work out if Solar Geocharging is noticeably reducing electricity consumption if at the same time, you have a PV roof that is doing just that, and has varying performance depending on the weather. Our prime target is to reduce the previous 2 yrs of energy consumption of 8500 kWh per annum.
The PV roof is giving us free energy for life, so you could say we do not need to do the Solar Geocharging... but hey! this is Research! Mrs NC and I and Ice Energy and my Professor Saffa Riffat, and my friends in EvoEnergy and Rushcliffe Borough council have great faith that this will demonstrate a chance to improve the performance of heatpumps.

Work continues: insulate, and pipes...

14 Oct : Yes, anybody reading this in recent weeks must think I have forgotten about the Solar Geocharging project. Well yes, the emphasis of the last few weeks has been on the PV, because it is such a major novelty (and expenditure!) But with the prospect of 3 students taking this on as a dissertation subject, I have to go ahead!
   I got the solar-air panels from Ice Energy in mid September, and they were in the garage for a few weeks. This week I decided to get back to work on the project. So I have recently bought some Loft insulation and have been topping the insulation from 20cm to 40cm. I use large insulation mattresses from Knauf, 1.1m x 3.6m, which unroll to cover the top of the rafters. This establishes the optimum height for the pipes that will go from the south wall to the north wall.
   I went to the plumbing merchant and bought £300 worth of 28mm copper pipes, elbows, tees, reducers, pipe insulation, and other essentials. The idea is for me to install the long pipes dry, and get a plumber later, for the glycol filling and connection to the heat-pump loop.

Tuesday, October 13, 2009

Perfect sunny day...

Sometimes you get almost the perfect day.... see the handheld meter - totally sunny in the morning with an unbroken bell curve... and only breaking up a bit in the afternoon with some very late light fluffy clouds, by which time the sun was well round to the west. It intrigues me how the roof picks up power, both by reflection off the clouds, but also by some sort of diffraction - when the sun is clearly round to the west and having no view to the east facing roof, and blue sky above it (nothing to reflect the light), the roof still picks up power and the meter notices when clouds float across.
Of course, if the roof faced south, the bell curve would be symmetrical with a higher zenith. I will photograph the curve at monthly intervals. With the sun low, the bell curve zenith must move to an earlier time of day eg 10am GMT, and in the summer I expect it to move closer to the centre, eg 11am GMT.
For this reading the OfGem meter actually recorded 13.01 kWh for the day, which must be as good as anybody can do for mid October. The handheld meter samples every 30secs and tots up an estimated aggregate, whereas the OfGem meter is always on.

Saturday, October 10, 2009

Green Energy Republic

10 Oct : I am just signing up for a beneficial tariff that goes through to next April 2010. This is provided by Good Energy, 15p per unit for every kWh we generate, even before we use it to send to the grid.
  We know we pay more for grid electricity with them than with the cheapest, but they are the only electricity company generating entirely from renewable sources. What we pay helps to support other home generators. See the BLOG called Green Republic which is a wonderful source of ideas and advice.

Friday, October 9, 2009

Fear of steep energy rise

Today, 9th October, one of the hottest talking points in the news is the OFGEM report on future Gas and Electricity prices. Both of these will rise steeply in the next ten years (even without taking account of inflation). Every time the prices go up, the urgency for householders to become small generators increases, and the payback gets quicker. There are different strategies for the next ten years, Dash for Growth, Slow Growth, Green Transition, Green Stimulus etc, but the only one that will keep prices stable is more of the Green Stimulus, where the government actively provides incentives to push people to being green faster than mere dissatisfaction with the size of energy bills.
It is an irony that one of the factors that will slow the increase in prices of energy is the increase in renewable sources, balancing against the increasing cost of fossil fuel.
Read more about the report in

Reply to Rushcliffe Reports Enquiries

I have had a few enquiries about the article in Rushcliffe Reports. One difference since the article is written is that we will use a cheap Swimming pool solar panel, not an expensive Flat-plate panel. The panels can be tee'd directly into the glycol loop using their own small pump and a non return valve (no need for an intermediate water tank). The solar panels are still in my garage; we have been focused on getting the Photovoltaics up first. The Earth Charging panels will go up next. The other enquiry is about the balance between Gas and Electricity - whether to use a Heatpump. Quick answer: You cannot be carbon zero if you use Gas. My regular answer to enquirers would go something like:

"If you can afford it, the combination of Heat-pump and Solar PV is a winner, we shall have free heating, hot water, cooking, lighting and power for life, plus an annual income (tax free), plus all our money back when we sell or leave to our children - even without the solar charging. The Solar Earth Charging idea is to see if the COP of the heat-pump is significantly better by finding warmer soil below - hence reduce electrical consumption. Even if it doesn't work, it's worth trying... but my professor boss says it is a wonderful idea and will work. It costs almost nothing because we are just using swimming pool panels, ideal for the temperature differences involved. Running cost is nothing, because the pump will only activate when it is warm, and our photovoltaic roof is earning enough to drive the pump."

"The house is so snug that it is almost boring, always 21 degC, and I could sleep in a summer duvet all the year round... except that my wife is a fresh air fiend and wants to sleep with window ajar, hence the need for an equinoctial duvet (medium tog) in winter... but we will never need a winter duvet unless there is a power cut for a prolonged time.. but then everybody will be in trouble if that happens."

Tuesday, October 6, 2009

Feed-in-Tariffs news

We have installed our Photovoltaic system entirely on trust that the proposal on feed-in-tariffs will actually be enacted in April, near enough as the proposal has been framed. There is a site telling you a lot about it - . There are a number of issues not finalised and the public have until Oct 15 to add more opinions. Some issues are:
• Existing systems should not be excluded
• The tariff levels are set on the low side
• Some renewables get a lower return than others
• Some types of renewables have been omitted
• Issues like taxation and index-linking have not been defined

I have sent in a reply to their request for consultation with my own choice of key observations,

• There is a need to increase the tariffs to a level that will encourage more participants. Even with a potential payback for my roof of about 7.5%, some people still think I am taking too much risk. It should clearly be enough to show 10% to push the public into making this investment.
• They should clarify the tax implications of the tariffs, and whether they will be index-linked. If the UK has a period of inflation, and it costs £30,000 to buy a sandwich then the tariff (presently framed at 36.5p/kWh for domestic PV) must logically be linked to the electricity price, e.g. something like 2.8 times the maximum price (presently 13p / kWh).  As the income for domestic householders is confined to 4kW, it will always be small, so it should not be reduced by being taxed.
• There is confusion about the 4kW limit for domestic PV systems. This is designed, for good reason of electrical safety to stop the DC output rising above 17amps. However, this could only be achieved on a south facing roof at 36º at midday in summer. I have a 4kW nominal system on an East Facing roof and even if we increased the nominal output to 4.5 kW (ie 25 x 180watt panels) we would still never be able to generate 4kW at any time of the day or the summer. So I hope they will allow a larger number of panels, provided that their angle and azimuth is such that the output could not exceed 17 amps.

Sunday, October 4, 2009

Rushcliffe reports!

Just as our first week of Photovoltaic living is completed, Rushcliffe Reports is published with an article about us on Page 11. Wow!

Actually I drafted this for them about 2 months ago, and the emphasis then was on the solar panel for earth charging. By the way... this is still going to happen, but one can only do so much at a time, and we focused on getting the PV panels up first. The solar panels for earth charging are in the garage and it's going to be a while to get them fixed on the wall and linked up. I have to find some 28mm pipes and lay these in the loft, ready for a plumber to make the connections. These are more difficult to find than I expected.

PV Solar Panels in Action!

The Photovoltaic panels are in action now, and generating electricity.

One psychological problem that I have realised I have to live with is that if you instal in October, you are going to see your system decline in performance for the next 4 months! It's like spending seventeen grand on a new car, only to see it performing worse and worse, until three months after buying it, it's only as fast as a bicycle! I can see why the new tariffs will start in April, it would be too depressing to have them start in October!

In its first week, we have had varied performance from it, from 4.5 kWh on a cloudy gloomy day to getting 11.5 kWh today (Sunday 4th) because of a bright sunny morning with fast moving clouds. I can see that there will be times when I am angry over a cloudy morning, followed by a sunny afternoon and evening... Let's hope those are balanced by days like today.

Friday, October 2, 2009

Displaying the results

We have a Schuco hand held display that picks up a wifi signal from the inverter in the loft. This shows the amount being received at that very moment, plus a graph of how it has varied between sunrise and sunset.
Even when cloudy, you get power so long as the sun has not set behind the clouds. They get no power in the daylight period after sunset.
The handheld unit shows the whole month at a glance, revealing a weather record of sunny and overcast.
This moment here shows the situation at 0920 on Oct 2nd with 1.4kWh already harvested under a cloudy bright sky.

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