The electric shed

[Theberylbloke]

Hi Optimark,

Yes, perspective is tricky. I've found it difficult to get a good shot of the shed simply because I'm likely to fall off the house pad before I get far enough away to get it all in the shot. There is 225 square meters on the main floor. The peak of the roof is 7m above floor level.

The woodworking section of the shed is planned to be under the lower roof on the same side as the panels. I was going to put dust extraction and air compressor on a small verandah on the opposite side of the building. Running compressed air around is not such a big drama but getting ducting for the dust extraction up and over the inside of the roof was not going to be easy. So I have a 3m by 3m extension going on the side for the dusty and generally less used stuff.

The shed was setup for the solar system. Google earth says I am about 20' 14" sth and the roof pitch was designed to be 20 degrees. It was also meant to have the long axis of the roof running exactly east/west (solar east/west, not compass bearing) for best performance. It is pretty close being about 4 degrees west of solar north. We have just hit 29kW per day of power produced. We will get more when I introduce the coconut palm out the front to my axe and perhaps the stand of small Morton Bay Ash on the neighbour's property as well. I have been quite impressed with the system's performance, even after the sunsets on the panels they kick along a bit until the last sunlight disappears off the hills. There is easily enough room for 6 more panels.


Alan,

Certainly won't win any awards for cheap sheds. I have a friend who said he would rather spend the money on a cheap shed and buy lots of machine tools. An equally valid view, I feel. It does have a few hidden virtues. When i decided i wanted a 500kG crane in the back of the shed and a 6m x 4.5m mezzanine above the crane (for office and general man cave), there was no grumbles from the engineer about reinforcing columns or carrying the weight. It was more "how high do you want that above the floor?" and "here are your plans!"

I told my builder I was going to enter it into the HIA awards for best shed in the under $200k bracket! He took out best house for $2m and best kitchen last year, so I reckon I'm in with a good chance! He reckons it will still be standing in 200 years time.


Cheers

The Beryl Bloke

[Optimark]

Pretty impressive power figures from that latitude and ambient temperature for a 5kWh system.

We are situated at 37.56S and have a 4.5kWh system, but it is spread over a north facing three roof situation. In the mornings we have four panels in sunlight pretty much after the sun is over the horizon, next a set of ten panels sitting on a flat roof with a tilt kit come online, followed by the last 4 panels waiting for the sun to come over the hip of the roof.

As a consequence of our situation we went with micro inverters, that is there is an inverter under each panel, 18 panels, 18 micro inverters. This has had some interesting side benefits, which we sort of knew about, but didn't realise how big a difference it would or could make.

As each panel puts out a slightly different level of power, whatever power they are generating we receive. We have 6 panels that pretty much put out 222-233 Watts in full sun at this point in time, the others are all between 210-215 Watts of output. Allowing for variations due to early and late shadowing we are streets ahead from our neighbour with a near identical system, but using one inverter. We guestimate the difference at about 8-10% more efficiency with individual micro inverters, however it comes at a 28% price premium over a single inverter.

The gamble we have taken is the differences in the power converted and the life of the micro inverters (guaranteed for 10 years) compared to a single inverter (guaranteed for 5 years). Supposed life expectancy of a micro inverter is 25 years as opposed to a life expectancy of 10 years for all single inverters that I could find in my searchs, we'll see.
'

Currently on good days we are converting around 21.5 - 22.3 kWh per day, up from around 15-16 kWh a month ago when the sun was lower in the sky.

My shed would easily fit inside one of your side wings!

Mick.

[Theberylbloke]

Hi Optimark,

Microinverters probably suit your roof space better than a single inverter. I would guess that microinverters would need to be more reliable as getting up on the roof to replace them is less straitforward than a single inverter.

I don't tend to get too caught up in the costs of solar systems. Over the life of the system and with power going up every year, I just figure price differences aren't worth getting one's undergarments in a knot, over. Our system was more expensive than most 5kW systems. That was due to the Installer we chose to use.

I went with that particular installer due to their OHS. The installer used a panel lift to get the panels onto the roof. The edge of that upper roof was over 6 meters above ground level at the time of installation. I understand most installers carry the panels up a ladder by hand. That might be OK on a low roof. The thought of having an installer carry 20kG of panel, over 6 meters up a ladder, by twenty trips was not a scenario I was going to buy into. One slip could very easily result in a fatality. Not something I want on my worksite. As an owner builder the OHS buck stops with me. Sure, it can be argued, the installers are essentially sub contracting to me and they are responsible for their own OHS. I was not prepared to run the risk of an accident. Who wants a serious injury on their job??

I run by the motto of "no one gets hurt today" and yes I'm anal about it. When the backhoe operator finished excavating, I shovelled up all the loose rocks and dirt and barrowed it out of the work area to reduce the risk of trips, stumbles, falls and twisted ankles etc. It was a few months before the concrete slab got poured and it was good to walk around on site without attempting to step over loose piles of dirt etc.

The installers told us to expect an average of 20kWh per day over the course of a year and up to 35kWh a day in summer. The 29kWh was on a perfectly clear day and we have had brisk winds over the last week or so which help keep the panels cool and the new roof helps keep the inverter cool as well. The panels also shade the roof cutting down on heat inside.


Cheers

The Beryl Bloke

[Christos]

What a very interesting update. I will continue to watch the process.

[Greywolf]

Just finished reading the thread, what a great looking shed ! I personally would love to hear some updates now we are almost a year on since the last post.

[Optimark]

Grey wolf, timely reminder as our system is 51 weeks old today.

As at 1330 hrs local time today, the system is currently generating 3,065.29 kWh hours of go juice.

The lifetime generation is currently 5,744.03 MW, essentially the generation for an entire year.

Looking at the plant viewer, we have 8 panels putting into the system power levels between 169W to 181W, the other 10 panels (at a different angle) are putting in power levels between 141W to 154W.

We don't have any fancy deals done with the power retailer/wholesaler, they had finished by the time we got around to putting our PV solar system. This fine with us as it is for the long term and short term would (may) have been nice, but long term is where we were at.

Essentially we have a price for all power consumed, that is the power we purchase our electricity for is one single price, which happens to be the most expensive tarif 24 hours a day.

We receive the same price, for all the power we put back into the grid.

As we generate, or have generated, more than we use, we are in front and our power into the grid is just generating enough to pay for the amount we purchase, plus it so far has paid for the daily usage charge, or connection fee as I believe it is called in some places.

For the first quarter of this year, we were a total of $37.00 (approx) in front of the total bill. For the second quarter of this year, we were in front of the total bill by $6.37.

Our last electricity bill where we were required to actually pay the electricity retailer was for the third quarter bill last year. Due to the solar system going online in August and the lower amount of sunlight available at that time of the year.

The fourth quarter bill for last year was pretty damned good, we were about $90.00 (roughly) in front of the total bill. By total bill I mean, the electricity we were charged for and the daily connection fee.

November and into the first two weeks of December were the best power producing time, I put this down to two things. Firstly the daylight time was getting longer, culminating in the longest day of the year in December the 21st. Secondly, the weather was certainly cooler, allowing the panels to generate more efficiently.

The best day we had, and there were about 4 best days, generated almost exactly 32kW of electricity on each of those 4 days. As the weather was just warm, not hot, we really put a fair bit of juice into the grid on those days.

From late December through to March, Melbourne started to get quite warm, in fact quite hot on some days. With the same amount of sunlight, but higher ambient temperatures, the system generated less power.

Within a three week period either side of the longest day of the year, but with much higher temperatures, power generation certainly dropped. The best days were all in the first week, to the second week of December, with each of those perfect sunshine and no cloud days generating 32kWh. From then on the same perfect sunshine and no cloud days, but with elevated temperatures, we just made 30kWh, a noticeable difference.

As an aside, I was in Germany in March and attended a power exhibition show/conference by happen chance. I heard one exhibitor outlining their systems ability to curb power input as the temperature dropped, which I found out is an important feature in that part of the world.

Essentially the power output of a solar system is so great in brilliant sunshine with an ambient temperature of -20ºC, that the system is in danger of pushing too much power through the inverters and blowing them to smithereens; something I had never thought about.

About two weeks before we arrived in Munich, the temperature at the house we stayed in, was -18ºC one cool morning, so it is a real problem it would seem.

One of the main reasons for installing our PV solar system, was to power an air conditioning unit on very warm days, or hopefully power our air conditioning system. I am happy to say the system more than compensates for the power consumed by the split air conditioning system. We can have it running, as well as the computer and some other stuff, and still be putting power into the grid on virtually any day with clear sunshine between 0930hrs and 1700hrs (daylight savings time).

We are quite pleased.

The real bonus though, is the payback time for the capital outlay. We originally figured it would be close to 8-9 years, maybe closer to 8, we weren't too sure. Current figures are telling us we will have paid the capital back around the 5.7 year mark, another reason to be pleased.

Mick.

[rusel]

Hi
Thanks for the detailed report, found it most interesting as we looking into put a similar system in.
Have you any thoughts on battery storage?

Will have another read through again before asking more question.

Thanks

Russell

[Greywolf]

Those figures are pretty fantastic !

I don't think batteries would such a good economic investment, since you are so far in front for 3 quarters of the year, that would offset the only quarter you aren't generating enough electricity to have an overall surplus. Factor in the cost and maintenance of a battery bank, and that you would no longer be selling as much and I would think it would be a net loss. If there ever was a time that you weren't selling back to the grid, then maybe batteries would make sense for nighttime/winter use.

[Optimark]

Battery storage is available, but from what I can see, not currently price effective, well, not at a price I could afford. My understanding is that within a decade, energy storage is going to make such a difference to our world; it may just be a little unrecognisable.

Photovoltaic energy collection is and will gain more ability to extract more power in the future, but not stupidly more power, more incremental gains type of power extraction. That is not to say it isn’t already possible, it’s just that the current stratospheric prices will probably hold it back; unless they start dropping.

Heat exchange technology is here and working, I actually saw working units in Germany in normal houses. There are various ways you can configure heat exchange, one is to use ground water for either cooling or heating, usually depth of whatever you require is the issue.

In the house I was staying in, in Munich, one requires a minimum depth of 60 metres before anything is possible. For another system, one needs about 800 square metres of land that has access to air, think grass or garden bed type of land. With many houses sitting on a land area between 500 square metres to around 700 square metres tops, that isn’t going to happen too much either.

Then there is an air-to-air heat exchange.

We stayed in a house that was reasonably new, about 3 years old tops. It is positioned about 800m above sea level, and almost on the Swiss border, but in Germany, cool winters are the norm, think around –20ºC to –25ºC as a normal cool spell in winter, with a few days last winter going down to –30ºC this February. In the summer time, as we experienced two weeks ago in this house, the ambient temperatures were in the mid 30’s, about 36ºC one day. That is an official temperature, not one taken from the back garden or verandah.

The house is a pretty standard German stand alone construction, it has a cellar, ground floor, first floor and using a ladder in the ceiling type of arrangement, there is also an attic, which in this case will probably eventually be converted into either some kind of room for a hobby or storage or whatever, but it is a reasonably small attic and is only in the central part of the house.

Where this house is a bit different from most houses built in the last 20 years in Germany is the wall thickness. Instead of the sort of industry standard 450mm thick walls, this house is running 600mm thick walls that allow greater insulation possibilities. The thicker insulation on the walls, ceiling/roof and cellar are there for a purpose, that purpose being to aid in helping the double air-to-air heat exchanger to work more easily, or to put it in another way, more cheaply.

The heat exchanger sits in the cellar in the engine room, so to speak. This room is about 3.5m wide by about 4m long. The water filtration system and water pumps are also in this room; they have to be otherwise there is a grave danger of the pipes freezing if they are outside. The house doesn’t have an outside water tap, one runs a hose from the cellar, or if there is water in the underground tank from rainwater, one uses that. The tank has it’s own internal pump, that tank is not small. Think medium sized inground swimming pool and about 4 metres deep.

In one side of the room there is a large cabinet affair suspended from the ceiling (concrete) it is the air-to-air heat exchange. This unit heats up the house with small vents in the ceilings of all rooms pushing heated air into each room; the vents are about 150mm in diameter. It also heats up the water, as in; it is the HWS heater as well. In warmer weather it takes heated air using the same ducts from the rooms, using that air to heat the HWS.

There is no cooling for the house, but there are electrically controlled roller shutters on all windows and doors and as the sun rotates around the house, roller shutters go down and up to keep the suns rays from entering the house via the floor to ceiling windows and doors. The windows and doors are all triple glazed, except the front door, which is a solid door.

The front door rates a special mention here; it has fingerprint technology to open if required. It was amazing to see the front door open after a finger was inserted into the groove and swiped downwards slightly. The door opens electrically, and I think, can also close electrically, but I’m not 100% sure about that bit. Nonetheless, the hinges for the front door are rated at 250kg each and there are 4 of them. Reminded me of a bank vault door opening and closing, solid.

Meanwhile back to the heat exchange stuff. An interesting conversation ensued between the owner of the house and the owner of the Munich house, father and son to be precise. Father to son about the heat exchange, “how much does it cost to run?” Son to father, “ hmm, the whole of last year was about 850 Euro to 900 Euro for the total electrical bill.”

Silence, as father and I took in what he said, then did some calculations and comparisons, and then we both questioned his statement. “Yep, that was the total electrical bill for the entire year”. That house is entirely electric and that is a phenomenally low electrical bill.

To put it into perspective, father, living in Munich in an almost identical sized house that is only 30 years old, but with 400mm thick walls as the standout difference, along with standard double glazed windows and doors, has an almighty fuel bill for heating, then there is the electricity bill.

A furnace in the cellar does his heating; heated water then circulates the entire house with exposed pipes along exterior walls and usually under windows. The system works well, the house is quite nice to live in and you only heat the rooms you need to use. The house has no cooling, which is pretty standard for German houses, we’ve been in quite a few, plus my wife is German and grew up there.

The heating fuel, they call it house oil; smells like kerosene. Costs them about 3,000 Euro to 3,500 Euro over the last entire year, not cheap. Then there is the electricity bill; I believe that bill is close to the son’s electricity bill. In effect, they have annual energy bills of somewhere between 4,000 Euro to 4,500 Euro. No wonder the father went to the energy conference, dragging me along as well, then put the hard questions to the son in hope of enlightenment and a cheaper total energy bill possibility.

Turns out the conversion cost for the Munich house may go as high as 20,000 Euro, doing the sums it seems a no brainer; conversion is probably going to happen. The Munich house won’t be as good as the Wollbach house, figures being bandied around suggest it will take about 15% more energy to see the system working.

Adding solar to both of these houses should see the Wollbach house become energy free, but at a pretty steep cost for PV solar, think double Australian prices for any system. The Munich house has a roof that doesn’t lend itself too well to PV solar, so that probably won’t happen, but it may.

Battery technology, according to the Germans, is already very doable, but there are different systems out there that seem to appeal to them as more advantageous and greener. The air-to-air heat exchange is the one that seems to be happening a fair bit in Germany right now, as far as I can see and hear that is, with my limited German and exposure to the general public over a three month stay.

Mick.

[Christos]

I read this once and I have to say WOW. This is quite an interesting topic.