rowanlangley (rowanlangley) wrote in green_power_gen,
rowanlangley
rowanlangley
green_power_gen

Variable performance over recent weeks.

Many days with overcast skies and rain, and typical yeilds of 1.5 KWh or less, with two days down to 0.6.

With the fairing up of the weather at the end of last week 4.3 KWSh was recorded on Firady and 4.0 on Saturday, comfortably in excess of the 1.8 KWh daily consumption with the surplus bringing about rapid recharging of the batteries - the batteries reached the absorb point briefly on Friday and reached the Float point on Saturday.

Completed the setting up and fettling of the solar hot water system in the old central library in Bermondsey. Embaraasingly we ran out of armourflex and were left with some parts of the pipe run uninsulated until further packs were delivered. This has a significant effect. What happens is that this results in a slug of cold water which is moved around as the pump runs, and one gets a reduction in panel temperature co-incident with the tank temperature starting to rise and often resulting in the controler stopping the pump as the difference has fallen below the minimum in the control settings. With all insulation now in place the pump was observed to run more or less continuously and the panel and tank temperatures were creeping upwards.

To take advantage I increased the cut off point for the tank temperature to 70C. AS the tank is a thermal store rather than one where the water is drawn directly, it can be allowed to reach a much higher temperature as there is a thermostatic mixing valve on the output to limit temperature plus all the showers have thermostatic mixers as part of the controls, giving two safety systems between the hot water and a person.

I have also brought the timer function of the controller into use, to inhibit the operation of the backup boiler from around 0810, when the last person is having their morning shower until around 1550, to allow the boiler to bring the store to temperature is required before the first resident gets home from work and wants a hot shower. The intention is to allow the last two showers to cool the top of the tank - it can fall potentially to around 45C before it becomes difficult to have the output water hot enough, and one hopes allows a significant amount of cold water to sink to the base of the store so that the store is most able to absorb heat, especially if the weather is indiffernt.
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