I’ve been recording the “Monthly Average” output from my PV system for a while (Since 2011). Looking at the figures for this summer. The “Sunniest” month was June (91 Watts), followed by August (83 Watts) and then July (81 Watts).
Ok, so July sucked, I think we all knew that. However what surprised me was when I looked at the results from previous years. It appears that the system has produced more power on average this year than any previous year.
To be continued…
So, having moved the garden shed and the PV panels in August/September 2011 to a more sun friendly position, I was pretty sure that there would be more output from the system over the next 12 months. Now, that 12 month interval is just coming to an end.
When I checked this evening, the average power generated 24×7 for the last 12 months as per rrdtool is 40 Watts, with a peak of 357 Watts. Which equates to approximately 350kWh, or somewhere between 70 and 90 Euro worth of Electricity for the year.
So in short, yes there was an increase in output, an approximate 42% increase in average power and a 100% increase in peak power. At least now I can tell myself it was worth the effort!
Some changes since last year. Firstly the panels have a different orientation from last year. I moved the shed last August/September and both panels are now facing South West (220deg), still at the tilt of about 5-10 degrees (which I really must measure), not ideal but better than before.
The same two Evergreen panels are in use, but I’ve a new Mastervolt Soladin Inverter from Nigel in Mysolarshop. Unfortunately I accidentally let the magic smoke out of the Steca, when moving things around and it had to be replaced. I might try and get the smoke back in some rainy afternoon when I’m bored. The measurement set-up is still the same using the Envi CC-128.
So for the last 12 months rrdtool is saying an ‘average’ of 28 watts is produced every day. So from the back-of-an-envelope, we get 0.028*24*365 or approximately 245 kWh produced, with a value of approximately €49.
However, I have reason to believe that output will be better this year. The first picture below is from the 3rd of June last year.
This one is from today:
Two things are immediately obvious. The peak instantaneous value, and the average are both higher. This should help increase the output from the system for 2012.
The experiment continues!
I (deliberately) flattened my iPhone today so I could charge it with its own charger. I about 19:00 I plugged it in to my kill a watt meter to see how much power it uses. I’m assuming the meter isn’t all that accurate, and as it is designed to measure typical household loads its display is in kilowatt hours.
With it plugged in for 19 hours with no load, the kill a watt claims to have consumed 240 watt hours. Which means that it would consume approximately 31.5 watt hours for a 3 hour iPhone charge time.
After charging for 3 hours the iPhone apparently used 40 watt hours, subtracting the 31.5 above gives a results of approximately 8.5 watt hours.
Given the inaccuracy of the devices, that is close enough to the 10 in my previous post for me to say about 10 and roughly in the ballpark of the previous test. Time to go looking for more accurate measuring devices.
A few weeks ago I was looking around the lab at the remnants of old projects and realised that we probably had enough bits to put together a solar powered charging station for phones. I.e. a 30 Watt PV panel (don’t buy from Farnell), a 12Volt Battery, and a PV charge controller.
I got an old 3 way cigarette lighter socket in Halfords, chopped the cable, added powerpoles, a fused connection to the battery and I now can charge my iPhone at my desk in work.
So, at break yesterday I was asked how much I was saving by charging my iPhone via solar energy. I had no clue, so I let my iPhone die completely last night and re-charged it while checking the charge current on a Watt’s up meter. I got tired of looking at it after 3 hours, but you can see the results on the graph below.
For the first 2 minutes, it stayed steady at 360mA, then the phone switched on and it started charging normally. About 45 minutes at 340mA, before the current started to drop away. At 20ma charging current I stopped the experiment. If we allow a fudge factor for the accuracy of the Watt’s up meter, and the efficiency of the Apple charger (I was running the test off a DC supply) and say about 10watt/hours, that translates to 0.00129 cent per charge or thereabouts.
So, after 12 months, what do the numbers say?
Well first a quick reminder of what I have running. A Steca Grid 300 from mysolarshop.co.uk, fed from two Evergreen ES-180RL 180 watt PV panels on the roof of the shed. They are fairly flat on the shed and not in an ideal location. There is about 5-10 degree of tilt on the panels. One of them is ‘facing’ South East, the other North West. So a very non-ideal situation, but useful nonetheless.
I’m using rrtdool to graph the output from an Envi CC128. The CC128 is measuring the output of the Steca grid-tie inverter.
So for the last 12 months rrdtool is saying an ‘average’ of 35 watts is produced every day. So from the back-of-an-envelope, we get 0.035*24*365 or approximately 306 kWh produced, with a value of approximately €55. Not a whole lot really.
Looking at the ‘average’ consumed by the house. It is now showing as 391 Watts (down from 455 the last time I looked). Giving 0.391 *24*365 or approximately 3425kWh (approx €620).
In short, its knocking about 10% off the electricty bill at present, not a lot, but given the panels don’t receive any direct sunlight in mid winter, it isn’t bad at all.
The experiment continues.
Winter is most definitely on the way, slight frost on the car this morning, and the weather station run by the South Eastern Amateur Radio Group showing a significant dip last night, though it was colder on Sunday night. Strangely though, I’m looking forward to getting a nice fire going on our new stove. And seeing how well it can heat the sitting room and the rest of the house.
I finished off the rewiring i mentioned in a previous post. This was mostly just a tidy up of the cables around the inverter. The inverter itself is an older model Powermaster PM-1500SL-24, however the battery charging circuit generates terrible Radio Frequency interference. This means that the shortwave bands are completely obliterated when charging is taking place (from either solar or mains/generator power), so I leave the inverter off unless I need it. I use a Steca PR3030 and two 80watt panels, facing roughly South, to keep the battery bank topped up.
I have tested the system it by running the central heating, fridge-freezer and chest freezer off the inverter for a few hours, but I must give it a more thorough test at some stage in the near future. The batteries are no longer new and, should there be a power cut, I’d better be able to keep the TV running or the boss will not be pleased!
From IEEE Spectrum,“My First Year With Solar”. Interesting how subsidies change the game entirely.
I was wondering the other day, how accurate the rrdtool graphs are. Currently the average shows is 455 Watts thus far this year (the graph stretches back to last October). So if the average stayed at this value for the full 12 months, what would my total kWh be for the year?
.455 * 24 *365 = 3985.8 kWh
As a comparison, I looked at my total kWh for last year which was 3940kWh. Pretty close I think you would agree.
Now, lets look at the average kWh from my Gorilla installation. Today, the average is 63 watts (since april). So,
63 * 24 * 365 = 551.88 kWh or approximately €100. If we put the price of the bits and pieces I have at €1500. That means that it would recover its costs in approx. 15 years.
Now, if, in our case, we consider the typical cost for a proper, grid-tie, 1kW Photovoltaic system in Ireland is about €4000. What would the cost recovery period be?
As the average sun-hours per day, per annum in the South East of Ireland is approximately 4 sun-hours per day, and the average consumption of our house is lets say 500watts (455 at the moment). That would mean we would recover 4 x 500 or approximately 2Kw of power per day from the system, with 2Kw going back to the grid, of no benefit to me (money wise).
2 * 365 = 730kWh or approximately €131. That gives a cost-recovery period of approx 30 years, ouch.
Assuming that my calculations above are correct, without a decent feed in tariff, PV doesn’t really make sense economically does it?
Been real busy at work with a project proposal. We finally got it submitted last Friday. Consequently I do not have as much done with the new machine to replace the dell dimension desktop. I started look at it today and I realised I had run out of spare sockets on the RIGrunner in the shack. So I need to sort that out first but it will require me pulling everything off the desk to do a bit of rewiring (sigh).
So rather than tackling that today, I first installed a 190 Litre Single Water Saver Kit that I got from ecostore.ie. It is 1/4 full already with todays showers. After that I moved my battery bank to its new home (with help from EI8JA). This is also going to require some rewiring to get the Inverter output back to the garage to hook back into the house wiring (where it moved from).
PV Panels are hooked up again, and the bank is being charged, but no AC available back in the house yet. Oh, lucky me, I’m “off” tomorrow, I wonder what I will be doing?