Thursday, November 26, 2009

Solar Rushcliffe Initiative Idea


25 Nov: On Dec 1 I am going to Rushcliffe Borough Council to present an idea about making a Solar Initiative in the borough.
I am doing a pilot study, developing a methodology for what could be a larger project, done by volunteers. I am evolving a Filemaker database structure, with the fields that would be required such as area, orientation, location. We could create a website that people could go to, to get information and register their interest.
    I am using Map-Photo analysis, combining Googlemaps and Bing.com aerial photography, and Digimap vectorised OS plans to map the roofs of West Bridgford, (and a bit of local knowledge) assessing them for building type, roof angle, kilo-wattage that could be installed. Main buildings, plus streets, plus some individual houses. Using local knowledge wherever possible. Perhaps identifying 500-1000 prime targets for PV generation. Nottingham Forest, Rushcliffe CC, Notts County Hall, ASDA, the Tennis Centre, Trent Bridge CC, some of the churches, and suchlike are all good for Larger installations. But then whole streets have house that are suitable… and many streets have hipped roofs in which none of the houses are suitable.
    The end result would be to have an informative website, and to write a very clear colour leaflet setting out the benefits, payback and costs, and then an individual form letter from the database to the householders declaring that their property has been identified in the research project as extremely suitable, and inviting them to ask for further details with a view to having their roof done (with a grant if before April 2010).
   To keep this simple, it is focused on Solar PV – which needs clear roofs. [Solar thermal can be fitted with little 2 sqm panels on any roof, and merely supplements existing heating systems.]
PV is answering the longer term need which is to reduce coal and gas burning for grid electricity.

Wednesday, November 25, 2009

Big Decision about the Battery

25 Nov : Also, after much agonising, and much time spent on design I have had to make a decision about the battery with the phase change spheres. I have at least two, perhaps three students dependent on me for a dissertation now, and I am aware that the battery brings two undesirables to the table: a big Delay, and excess Complexity - both of which are bad for them, and bad for me too.

To prove my basic hypothesis that the ground can be warmed to counteract its heatloss, the best route is PLAN ONE, which is to take the solar and air heat directly to the boreholes.

The other reasoning behind this decision is that the Delta-T between the Solar-Air panels and the Ground is perfect. For the battery idea to work perfectly, I would really need a high temperature flat-plate solar panel, as I would have if using a large tank of water. If I did that, I might as well go the whole hog and have my original idea (of a large water tank), which would also have reduced the cost of warming the domestic hot water. With the PCM balls in the battery sticking at around 23º, the panels would not often be hot enough to send warmth to the tank - whereas when comparing with the ground temperature of 8-13ºC, the Delta-T is favourable for most of the year, even at night.

Since a part of my idea is to see if the low-cost low-temperature air panels will do the job of warming the ground, then the use of a battery or tank introduces a level of complexity that is just too confusing. I will retain the balls and consider making the battery in a year or two. (The balls can be stored in the loft until then, and it will be easy enough to plumb in the battery in two summer's time.)

More solar collectors arrive!

Nov 24: Back to the Solar Earth Charging.
I have been waiting a while for the remaining two black 'Solar Focus' panels, and they arrived today, in an Ice Energy van - so I now have all four and can get on with the next stage - scaffolding the exterior to set them on the wall and connect to the interior piping.
     I will probably use the same scaffolders as did our house for the PV solar panels. Apparently a normal contract time for the scaffolding is a few weeks, so that gives enough daylight hours to get the holes drilled, etc.

Tuesday, November 24, 2009

Solar Surfing the Web!

24 Nov : The SunnyPortal website can be very revealing, if not fascinating. It leads me to think that it could lead to a dissertation topic in itself - by revealing 22 thousand sites all over the world, there are a wonderful range of systems all reporting themselves to the web - not just domestic roofs like ours, but others more revealing or experiemental.

There are combination ones (so you can compare wind and solar on the same site with the graphs combined). There are some experimental structures (eg solar panels on trees of metal tubing, motorised structures, or ones that build mirrors alongside the panels.) A student with enough patience could identify many interesting installations, and then follow up by contacting the owners for more detail in the case study.

RS485 Nightmares and Web Talking


Nov 24 : Our system has been talking to the web for a week now, by sending data to the SMA Website. The SunnyPortal.com compiles the data into graphs. We lost a few days of data over the weekend when the data cables pulled out of the plug when modifying the way that the unit was screwed to the wall (although the roof kept on working of course). As the colour coding of the strands was unusual (check RS485 on Google), I needed to experiment with the colours, and ask EvoEnergy a few questions. Got it working by Tuesday lunchtime after three very frustrating hours of trying.
    Now I am having interesting times configuring the pages on the SunnyPortal site, because you have limited desktop publishing abilities to very the appearance of the graphs - bars, XY points, lines, polygons etc. We have also enjoyed the addition of a sensor that gives Daylight levels, surface and ambient temperatures. Sometimes, this can allow one to reflect, eg when the surface and air temperature are close the wind is less, and when a strong SW wind is blowing, the temperatures diverge.

Tuesday, November 17, 2009

Peveril Solar roof is on line!

Nov 17: Kevin and Dan from EvoEnergy spent a bit of time at the house completing the installation of the link from our solar PV roof to SMA's ftp site on the internet, with Dan doing the hard work of reading the manual, and trying to work all the network settings.
     The Schuco inverter and SunnyBeam transmitter box come from a German company called SMA, and now there is now a live information feed from our router to the SMA server. SMA's website then stores and re-broadcasts the info to anybody who cares to see. So here is the graph of our roof, http://tinyurl.com/peveril-solar-roof. The info is blocked to quarter hour intervals, and takes about 45 mins to be compiled to graphics (and seems to show continental time). But it's great to have a display that builds up the calender of previous days, weeks, months and more.
It has been hard to manage without the hand held unit, and it is a sorry fact that the inverter doesn't allow one to use Both the Handheld and the Web display. But we went for the Web connection, as the widely visible display and record keeping is more important.
I see that our installation gets a mention on the EvoEnergy wordpress Blog.

Monday, November 16, 2009

Let the Plumbing begin!

Nov 16: For some weeks, I have been working out the lengths and dry jointing pipes in the loft. This weekend I finally soldered some of these, so the arrangement of panels is now fixed! These are all at the South end, and the panels will be on the external side of the wall. Yes, maybe they are a bit rough (all soldered, no Yorkshire or compression fittings...) but I don't think they will leak.
    I also began making one of the copper elements for the thermal battery, although in some ways, I wish I hadn't discovered those PCM balls, my life would be simpler if the Solar-air panels were just directly connected to the ground. It is isolatable, so if the battery never works, it doesn't matter hugely, as the system can run as originally intended. I feel so strongly curious about it, that I am prepared to build the thing, and see what happens.

Wednesday, November 4, 2009

3D Model of the thermal battery

Nov 4: I have been working on a 3d model of the 3D battery and elements, not just for fun... but it looks better for illustrations on the blog, and will help me in the fabrication process. It helps in finally deciding the positions of pipes - the copper elements have to be fabricated outside the tank and lowered through the holes in the lid.... and must be designed so they won't settle in the tank, or get air bubbles in them.

The outer pipes are 28mm copper, and the cross pipes are 15mm, to give some distribution of glycol, without having a short circuit. Also, the cross pipes enable me to fix legs which will keep the elements at the right height and slope.

December postscript: I have returned the plastic water tank and ballcock to Screwfix, but will retain the spheres and will have a go at this in summer. I will put in Ballvalves at the point on the pipe where the battery could be inserted.

Tuesday, November 3, 2009

Discussion with Ice Energy: Bottles

Nov 3 '09: After meeting Chris, I had a phone conversation with David Atkin of Ice Energy. I explained the changes in the plumbing for the panels which he seems satisfied with. He had some important points to make about the positioning of Expansion bottles, air release valves and Glycol top-up bottle on the plumbing diagram.
   The new plumbing arrangement gives more equal share to all the panels, but one can also control this with Valves (normal screw down ones) which is how a plumber balances heat distribution in a central heating system. The diagram and panel arrangement now equalises all the panels, so that there is no need for controlling valves which would present yet more restriction for the liquid flow and cause more work to the pump. In this diagram, hot glycol from the panels can never get directly to the heatpump, it has to circulate through the boreholes first, or through the battery of PCM balls, depending on the setting of the valves.
I only have two of the Solar Focus panels, so I need to visit Oxford to get the other two, or have them shipped up to Nottingham.
Another question will be about the speed at which to run the pump. Sluggish, or quick?

Meeting Chris Wood: Diurnial, Interseasonal and 5 yr cycles

Nov 3: in my meeting with Chris Wood, we also discussed the way that heat stays or moves in the ground, relative to the boreholes. He has done tests with sensors at different distances from GSHP borehole pipes.
Diurnial: We drew a diagram, a bit like ripples on a pond of the heat moving out from the borehole centre to the surrounding layer, showing that on a day-night basis, the daytime harvest of heat has nowhere to go than back up in the evenings, and any surplus moves out through the rings. The thermal curve is modified and will be added to this blog soon.
Interseasonal: This is very interesting, as we both know that the ground immediately around the pipe gets cooler month by month, and in Feb-April when the ground is at its coolest, the heatpump is having the most difficult task with cold ground - this is when the immersion heater element of the heatpump comes on, and ruins our Coefficient of Performance (CoP). During the long summer (with heatpump only drawing a small amount of heat for domestic Hot water) the ground recovers. However, in this spring period the sun is shining on the surface and if we can send solar heat down directly, the curve is changed. (See diagram - the area around pipes gets colder).
During the remainder of the summer when our solar heat is put down enough to exceed the heat taken out for hot water, some of this surplus heat may fortify the ground for the long winter.
5-10 year cycle: Chris explained how the ground gets colder year by year. It can be represented by a declining SIN wave. After each year, the highest temp that the ground recovers to in summer is never as high as in the previous year. Eventually it reaches a new stasis - this could be 5-20 yrs after installation, depending on the conductivity of the soil and the size of the house pulling heat out.

If the Solar Geocharging raises ground temperature, this will be remarkably successful, but is unlikely. What is very desirable is that the SIN wave has the same nadir (bottom) year after year (instead of dropping), and perhaps we might achieve a higher zenith - if this occurs, and we discover that it will maintain or improve the heatpump's CoP at that of a new machine in new ground, that will have been worth achieving.

Meeting Chris Wood: Panels and Balls

Nov 3: I had a meeting with Dr Chris Wood (recently of our Department, and currently on Knowledge Partnership project with Roger Bullivants). He is very interested in the project and has many pertinent comments to enrich the project, both for Solar Geocharging and for the use of a Thermal Battery.

Balls: He took away one of the Phase Change spheres to conduct some tests on, eg to use a testing tank to estimate the actual thermal capacity of the ball and the phase change temperature. As we dont know where they came from (we think they came from China for a chinese PhD student to use for research) we can use his tank test to discover their specification retrospectively. If the Balls are unsuitable, we can use the Thermal Battery using other phase change material such as brickettes of Wax, Water, or PCM emulsion from BASF.
Panels: We discussed the flow through the panels and although I now have a 'parallel' flow through all of them, this is going to favour the western most panel (left hand) too much, risking a short circuit that leaves the rightmost panel cold.
So, we redesigned the plumbing to make a more equitable arrangement, grouping them in two parallel pairs, each pair being sequential in flow. All the panels exit and enter from the top end, with airlock valves in the loft to prevent air bubbles.

Post script with hindsight written 22 April 2010: I am trying to work out when the polycarbonate boxes first appeared - it is clear from this elevation that they were not in the frame in early November 2009.

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