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Renewable Energy generators' Journal

Saturday, March 10, 2012

4:20PM - Renewable energy reports :

Bermondsey. 10-03-2012

Climbing to around 4 KW under the overcast sky in the morning
Peak power of 8.5 KW during early afternoon.
Building exporting between 3 and 5 Kilowatts

Thursday, March 8, 2012

10:16AM - Renewable energy updats

Harrow.

Half a kilowatt and it's only 1000.
Around half the consumption is from solar at present. Several days everything runs on the solar supply, with loads being shed after indifferent days to allow the surplus on days like this to bring the battery charge up again.

Generally the cue to return fully to solar is when the log from the controller for the days shows significant time spent in "Absorb" mode, as this the the mode where the last 20 per cent or so of the possible charge is being stored.


Bermondsey
All commissioned, and Monday was reported as producing 5KW at 1000. The system is unusual in having panels horizontal. This is not my choice, but it did keep everything invisible from ground level and allowed things to go obtain planning and listed building consent. The power loss from a flat mounting is offset to some degree by being able to fit more panels into the available space. This gives a payback in poor sun conditions where there is more light coming vertically from scattering in clouds, and there is a greater area of silicon to capture it.

Under poor overcast systems a kilowatt of power has often bee recorded.

Tuesday, February 28, 2012

8:42PM - The big system

Commissioning over the weekend was successful - Array wiring all proved out Saturday, tested to the input plugs to go in the inverter, then one link disconnected each array section to leave it in a safe condition as there was a chance there would be work done on sunday adding the remaining ballast blocks.

Returned late Sunday afternoon, restored the links, rechecked the array volatage and polarity, set the inverter to G83 and English and connected everything up.

Self test was successful. System fully commissioned Monday and registered. It wrung 11 KWh out of indifferent sun on Monday and 22 KWh today. At mid day the building was exporting power.

A pleasing conclusion to five weeks work.

Thursday, February 23, 2012

9:09AM - Nearly there

Panel frame being levelled
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Trial panel fitted to check fixing methods
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Frame now all level and ready for panels
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Panels installed ready for connection.
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Inverter room with wiring nearly completed
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Inverter room all complete
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Saturday, February 11, 2012

7:48PM

2.4 Kilowatt hours harvested today
Yesterday a peak current of 26 amps when the sun came out at mid day.

The cold snap is proving a good time for winter solar electricity, with good harvest of over 2 Kilowatt hours on several days during the last fortnight

Sunday, January 15, 2012

10:00PM

Sun conditions excellent.
1.4 KWh received.

Soure of power loss found and corrected - large shrub in garden which shades the west section pruned.

Saturday, January 14, 2012

8:22PM

Even better weather today
1.4 KWh.

Free electricity tonight

12:03AM

Good weather today - clear sky and low temperature.

1.1 KWh harvested

Wednesday, January 4, 2012

9:58PM - The big system

Orders just placed for cables switchgear and meter for a 10 KW 3 phase grid connected system.

reviewing quotes for inverts and PV modules.

Doing lots of calculations for roof loadings, wind forces and playing e-mail tennis with structural engineer

Sunday, July 31, 2011

2:22PM - Maintenance day

Very little required.

however, mid day current of only 17 amps seemed rather low for a summer day, and inspection showed a number of cell shaded by the brambles. Once the secateurs had done there work a current of 21 amps was recorded.

Cooking lunch with the steamer produced a peak current of 25 amps out of the charge controller, which dropped back to around 21 amps or so. For the first time in around 2 weeks the batteries have had a period of "Absorption" charging rather than "Bulk".

I also nailed an annoying RF interference issue spoiling my enjoyment of radio three. The link from the DC negative to earth has been re-made and the inverter negative cable dressed clear of the actual inverter - it seemed to be prone to picking up interference from the innards of the inverter and forming some sort of feedback loop.

Saturday, June 11, 2011

11:23PM - The year so far with the new system

Very good results so far.

I have not had to buy in energy electrical energys since march
Since the last week in March my little secondary meter unit (an "Efergy" shows

7 KWH for the end of march
45 KWh for April
45 KWh for may
17 so far for June

A total of 114 KWH delivered and used from the sun.

Sunday, April 24, 2011

12:12AM - Absorb time and cut off current

Took advantage of being at home in the day to do some further investigations.

The Absorb part of the charge process is important. It is responsible both for getting the final lot of charge into the battery and preventing the water in the electrolyte breaking down, giving off hydrogen and both creating a hazard from explosive hydrogen and making the electrolyte excessively acidic to the detriment of battery life.

If the battery spends too short a time on Absorb it will never become fully charged and over the long term sulphation is a possibility.

If the absorb time runs on too long then the battery will be driven into overcharge.

A time limit gives an overall protection from overcharge and can usually be set with the aid of the manufacturer's data sheet or tech support.
The aim is, however to end the absorb stage when the charge current drops below a critical threshold.

in a system such as this there is both charge current and load current to be considered. The load current must not be allowed to mask the charge current and cause the controller to maintain the Absorb voltage past the point where the battery is fully charged.

By connecting and dropping the load it was possible to observe the standing current of around 2 ampere from the daytime base load.

Around 5 amps, the battery is fully charged, and the tracking process starts to introduces sufficient variation in output current that it appears that the charge point may not be detected reliably.

As a trial the cut off current for the Absorb cycle has been set to seven amps, with an overall time limit of 3 hours and this will be observed over the next few weeks.

Thursday, April 21, 2011

8:34AM

Yersterday :
Energy in from the sun : 2.9KWh
Energy consumed : 2.2 KWh

Grid remains out of use

Wednesday, April 20, 2011

10:36PM - daily

Yesterdays totals
In : 2.9 KWh
Used 2.14 KWh

Today 2.9 KWH harvested, 3 hours absorb, 1 hourr on float charge
Plenty of stick given this evening : fresh vegetables in the steamer, rinse and spin some washing in the machine, and naturally a cup of tea.

Tuesday, April 19, 2011

9:50PM - Renewable energy reports.

yesterday - solar energy in 2.5 KWh, consumption 1.7 KWh

today, 2.9 KWh, three hours "absorb" charging, suggesting the battery bank is close to replenished after the dull week last week.

Monday, April 18, 2011

6:18PM - Another week off the grid

Typical daily havest is between 2 and 2.5 KWh.
Typical daily consumption is around 1.5 KWh with a day up to 2KWn

Lowest daily harvest was 1.1 KWh, with a consumption of 1.3.

Most days show a surplus of around 0.5KWh

Tuesday, April 12, 2011

8:16AM - The story so far

Generating conditions picked up around mid march. Daily yields started to reach the 1KWh mark, and most days this month the figure has been 2KWh or more.

A typical day this month collects 2.5 KWh from the sun and the secondary meter shows somewhere between 1.5 and 2KWh consumed in the flat from the solar. The meter for the grid sits at a pleasing 0.00 virtually every day.

A the last major part of the upgrade was performed on Saturday when the temporary cables from the battery bank were replaced with the new cable assemblies ordered from CCL and Barden. There are 50 sq mm in cross section area. Voltage drop under heavy load has now been reduced from over a volt to around 0.25V.

Sunday, March 27, 2011

8:49PM

The new system is bedding in.

With a serious investment made in a new battery bank I have been in no hurry to throw load at it, and instead used the daily logging c=facility on the charge controller to build up some solar data.

Taking a usable day as a solar approaching 1KWh,
Back in January and February two days in every seven would count as usable,
Not much differnece in early March,
Steep improvement from the middle of the month onwards, with the best day so far being the 19th with 3.3 KW hours harvested. Most days since then showing generally above 1.5 KWh.

The present task is tuning the charge controller settings to the battery bank.

The bulk charge is when the controller throws all its energy at the bank, subject to the current limit programmed in or set by the sun conditions. During this time the terminal voltage of the battery bank rises as energy is absorbed.

The data sheet specifies 28.8 volts as the absorb point, so the controller is set so that when this point is reached the voltage is regulated to this value - allowing it to go higher leads to overcharge, breaking down the water into hydrogen and oxygen and shortening battery life.

As energy is absorbed the current drawn by the battery starts to fall off, this has been observed over time.

Up till now I have exercised caution and not altered the time of one hour which is the figure as shipped from the factory. This will, however mean that after an hour the absorb stage is terminated by the controller regardless of the actual state of charge, whereas the behaviour required is either the absrob part terminating when the current has fallen to a low figure, with the time set to give a backup protection against overcharge.

The equation set out in the data sheet gives an absorb time between 6 and nine hours depending on the limit imposed on the charging current. I have increased the time to 4 hours to start with as both the input power from the array increases and the operating time is also increasing.

Once the absorb cycle completes the charge controller reduces the applied volatage to the float voltage (set as 26.28 as in the battery data sheet) which is sufficient to maintain the level of charge but is too low to allow any significant charging current to flow.

Sunday, March 6, 2011

3:47PM - Solar readout example

The charge controller readout this afternoon

Tea being brewed

The controller was working the array hard to get nearly 20 amps towards the 83 Amps required for 2 KW at 24 volts at the inverter input.

PV Renewable energy

2:43PM

By 1400 today the sun had already put 1.5 KWh into the battery bank, a whole day's worth of electricity already, so it was the solar electricity which went into the kettle for tea.

The new charge controller is earning its keep and today it wrung a charge current of 33 amps out of the early spring sunshine, something the last setup could never manage. It also gives me much more information about its activities each day - total energy in from the sun, also the total charge which has passed through, together with the peak output current and power, and peak array voltage. It also records the time (if any) the battery bank spent under "Absorb" and "Float" conditions.

For much of February the array has been left just for battery charging / conditioning with the charge controller logging giving some useful data on sunshine patterns. There seems to be a pattern of about two usable days out of five during the winter period.

Loads started to go across towards the end of February. The kitchen sockets went first. The loads are intermittent, allowing plenty of time for just battery charging during the day. All the selectable circuits went over to Solar yesterday evening after the controller recorded a run of good days during the week.

Meanwhile a general slow down in trade and possibly manufacturers starting to see some return on their (considerable) start up costs see trade prices for PV modules edging downwards toward the £1.50 - £1.70 per peak watt level

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