Category Archives: Green

Shack 2.0

So, several months later, house move complete and it is time to get a shack operational again.

I am a fan of keeping things running when the power goes out. From a Amateur Radio Communications perspective, I have had a 80Ah battery in the shack for over 10 years and I have been using a West Mountain Radio Super PWRgate PG40S and Rigrunner 4010S to power my radio equipment and to keep the battery charged. My current ‘desktop’ is based on a Intel NUC 7i7BNH these along with their LCD’s are running off an older APC Smart UPS 1500, which gives between one and two hours of run-time should the power go out.

While everything was in boxes, I purchased a West Mountain Radio EPIC PWRgate (I wonder what adjective will be used to describe the 4th Generation!) this device can charge Lead Acid, AGM/GEL and LiFePO4 Lithium battery types, and, what attracted me to it is that it has a built in Photovoltaic (PV) Charge Controller. Which removes the need for a dedicated Charge Controller.

Sometime during the move, the old AGM battery died (Ophelia was its final ‘performance’). New shack, new battery, a Trojan EverExceed ST-1280 was ordered from O’Connell Batteries in Cork and duly arrived.

Plug-and-play? well not-exactly. After looking at the specs, the default ‘AGM’ setting in the Epic PWRgate needed some adjusting to avoid overcharging the battery. The battery specifications say 2.35 Volts per cell (for 12 hours), so the ‘Max charge voltage’ needed to be dropped from 14.4 to 14.1 volts, and the PSU set to 14.2. On Linux, the Epic PWRgate appears as /dev/ttyACM0, guessing I used 115200, N81, no handshaking and its console immediately popped up.

Battery:  1-Disable, 2-Gel, 3-AGM, 4-LiFePo4, 5-Other:    <3>: 3                
Reset to default values (Y,N):   (Y,N) <Y>? n                                   
Max charge voltage in Volts:    <14.10>:                                        
Max charge current in Amps:    <10.00>:                                         
Min charge current in Amps:    <1.00>:                                          
Trickle current in Amps:    <0.25>:                                             
Recharge voltage in Volts:    <13.49>:                                          
Max charge (minutes):    <720>:                                                 
Retry after abort (minutes):    <240>:                                          
Min supply voltage for charging in Volts:    <14.15>:                           

Once out of setup mode, it spits out readings about once per second. This includes what the state of the chargers is, the power supply voltage (PS), Battery voltage and charging current (Bat), Solar Panel voltage (Sol), Number of minutes in this charging state (Min)

 Trickle   PS=14.22V Bat=13.61V,  0.05A  Sol= 0.04V   Min=962  PWM=337  adc=6                                                    
 Trickle   PS=14.22V Bat=13.61V,  0.05A  Sol= 0.04V   Min=962  PWM=338  adc=6                                                    
 Trickle   PS=14.22V Bat=13.61V,  0.05A  Sol= 0.04V   Min=962  PWM=339  adc=6                                                    
 Trickle   PS=14.20V Bat=13.62V,  0.05A  Sol= 0.08V   Min=962  PWM=339  adc=6  

Hopefully the battery is as reliable and lasts as long as the last one!

Irish Summers getting brighter?

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…

Micro PV

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!

Micro PV two years on.

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!

iPhone and charging

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.

iPhone and PV charging

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.

Micro PV, one year on.

So, after 12 months, what do the numbers say?

Well first a quick reminder of what I have running. A Steca Grid 300 from, 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.

First Light

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!

Averages, and another Gorilla update.

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?

C’mon Munster!