SteamyTea

It is always worth knowing why you want to monitor something as this denotes what you can do with the data. Let us take a simple slab as an example. You can just put a sensor in the centre (but which centre) and sample the temperature every day at the same times i.e. every hour. On its own, that will not tell you much. All it will record is the temperature at that point at those times. It has nothing to relate to. So let is add another temperature to do room temperature. So where do we put this one. Hanging from the ceiling so that it is in the centre of the room (assume it is a simple rectangle floor plan), or hide it in a corner, maybe at seat height, or low down, under a sofa or fridge. Will it be affected by sunlight, draughts, mechanical air extraction? Once you have sorted those out, you can now start comparing your two data sets. There are 3 main ways to do that: Temperature Difference Binned Mean Temperature Data Sets (quite tricky to set up) Time Series Data They will all give you different results, so you need to know what you are doing it. But that still only gives you a comparison between two points at any given time (slab and air temperature), so it is probably worth getting another sensor to do external temperature (or a local weather station to get data from). Even then, it is only comparing temperatures and with a relatively large margin of error (there are statistical methods to show the bounds that are easy to set up and use). The trouble with just measuring temperature is that you will not know if, it is the internal air temperature, or the external temperature that is affecting your slab temperature, or the slab temperature that is affecting your internal air temperature, as they both may be affected by the external temperature, or the insolation, or maybe the wind speed (has a greater affect than anything else at my site). So you can see that is quickly becomes tricky to know what to measure, and when, where and how. Now two simple scenarios: Control internal air temperature from slab temperate Establish relationship between slab temperature and internal air temperature To control internal air temperature from the slab temperature is quite simple, you just plot slab temperature along the x-axis of a chart, and internal air temperature along the y-axis, draw a line of best fit (spreadsheets are excellent at this) and you will end up with an equation (stick to a simple straight line y=mx+c). As you have forced the 'controlling' factor, the slab temperature onto the x-axis, by knowing that temperature, you can just read of the chart what the air temperature should be (there will be margins of error). So if the slab gets cold, you heat the air, if it gets hot, you cool or replace the air. Simple, but crude. Much easier to just control the air temperature from the air temperature, it will be more accurate. To establish relationship between slab temperature and internal air temperature is really just a matter of collecting enough data and plotting the slab temperature against the internal air temperature, but without, or allowing for, external factors. So no heating, cooling, bulk air movement (sealed room), then look to see what the time difference is between changes. So you can start by slicing the data up into seasons, months, weeks, hours of daylight, intensity of sunlight, wind direction, wind speed, rainfall, curtains opened or closed, room usage etc, and just compare that to the 'sealed room' data. This will usually need the logger set up differently, so rather than sample at fixed times, you sample at fixed temperature differences i.e. every half degree. Then you look at the lag times, these will usually overlap because of the differing thermal properties between the slab and the internal air. You can then start to interpret the data and see where the variances are, but you still need to know why you are doing it. So assuming that it is for internal temperature control, you can create a large data array that allows you to set the heat input parameters i.e. how much and how long to heat, from the historical data i.e. slab is 2°C below optimum, I need 3 kWh of thermal energy in the room in the next 7 hours, or whatever. So after that ramble, decide why you are doing it first, then how you will do it, then what you will do with the data. Before long you will be an expert at conditional data manipulation.

Start reading: https://www.gov.uk/government/publications/electricity-market-reform-contracts-for-difference I think there are several different ways that a PV generation company can sell their produce, just a case of someone sitting down and working out the best contract to be on. If you take out the CO2 element, they are just like ordinary, small scale, producers and can enter the auctions when the price is right. So they may elect to just sell power for the morning and evening peaks in the summer and give power away the rest of the time. This, if there is enough solar being generated, will affect the market price. That is a risky game to play though as they may have to 'buy in' power when they cannot supply, and that will be very expensive as it is calling on the 'hot spinning reserves'

Have you really forked out nearly £50,000 before you actually start the real work?

I come from a production engineering background, I don't see that as a problem.

If you are using a lot of timber on site, and most houses seem to have more timber than anything else, why not buy a cheap, but adequate, planer thicknesser and save yourself a lot of time and hassle.