Going Off Grid - Powering house and cars purely with renewable energy
by, 08-28-2013 at 01:20 PM (20686 Views)
This is my first attempt at a blog and one that will likely stretch over the next 18 months or so as I find my way through this project. During that time I'm going to see if it's possible to not only install solar power but also to get to a point where we can disconnect from the grid completely.
At our previous house we installed solar PV panels with micro-inverters on a net-zero system. The full story was outlined in a TMC post about 2 years back and you can still find that here. At the time micro-inverters were the best option for us given the limited space we had and my obsessive desire to keep an eye on each individual panel.
The net-zero system basically means that you spec the size of the system to cover your total power requirements and during daylight your meter runs backwards as you return power to the grid; the meter then runs forwards as you draw power from the grid at night. Hopefully, if you got your sums right youíll net out owing the utility company zero.
Since that install we have moved house and technology has moved forward so Iím starting over on our new house with a different set of ambitions and circumstances.
We now drive two electric cars, the Tesla Roadster and Model S, with a reservation on Model X (Iím not sure I can justify 3 cars, so the Roadster will likely go when Model X arrives) and Iíd really like them to be powered totally by renewable natural resources. I want all our energy requirements to be covered by our PV system but ideally weíll generate and store our own power to disconnect from the grid completely. Iíve investigated various alternatives for battery storage/back-up but didnít find an option without replacement and recycling issues; however, as technology advances itís looking like we have options to disconnect from the grid completely without fossil fuels and that is too good an opportunity to pass up.
Living in SW Florida we average 304 days of sunshine per year. Our new house is kind of colonial style but has a roof that could perhaps be described as a higgledy-piggledy; not conducive to nice rows of PV panels.
We have a barn/shop that has a perfect, sloping roof but less than ideal elevation and we have plenty of space with around 10 acres of pastures. We are planning on moving horses onto our property (my daughter rides competitively) and thatís going to require building stables (this becomes important).
The house is a fair size and we run 3 AC systems basically year round as well as pool pumps etc. so total electricity costs are around $5,400 annually. We currently have solar heating for the swimming pool and a roof based solar water heater for the bathrooms.
Our water supply comes from an underground aquifer, is unlimited, and is free (this also becomes important).
PoCo Meters & Rebates
An oddity of our set-up is that we have two electricity meters. One residential meter for the main house and one business meter on the existing barn with load split between the two. Coincidentally this offers us the chance of substantial rebates which we could not otherwise access. Weíre going to need to balance the loads between the 3 fuse boxes and 2 meters in order to gain maximum benefit but the cost of the electrical work will easily be outstripped by the rebates gained.
As we have to bore some lines from the new stable and the existing barn/shop to the house weíll just put an extra conduit at the same time and that will help keep those costs down.
There are no state subsidies or rebates programs in Florida; but there has been a long-term rebate program operated by Florida Power & Light (FPL) our local utility provider. The next round of the rebate lottery takes place in October and grants rebates of up to $20,000 for residential systems and up to $50,000 for commercial systems. Needless to say, there were big smiles around here when we discovered that we are eligible for both grants due to our dual meter set-up.
- Generate power from a solar PV system
- Use that energy to separate hydrogen from water via electrolysis
- Use a hydrogen fuel cell to power the house
This graphic which Iíve borrowed from Verde LLC demonstrates the idea nicely:
If we size our PV system appropriately we will have the ability to generate excess hydrogen during daylight hours and then store it to use it at night and during low-light periods. Residential hydrogen generation and fuel cell use are at early stages of development but weíre already in contact with 3-4 different potential vendors; however, the FPL rebate plan requires us to run a net-zero connection for at least a year prior to going off grid completely, so we have plenty of time to explore this.
First Steps, First
Water coming out of the ground was not really suitable for drinking; it wouldnít kill you or even make you sick but there were high levels of iron, a light sulphurous smell and very hard water which left water spots and stains on every surface.
I installed an Iron Curtain system from Hellenbrand to deal with the iron and sulphur, a chlorinator to kill the bugs, carbon filters to remove the chlorine again, a water softener and finally a Sterlight UV tube to kill anything that might have escaped the rest of my firewall. End result is water that is purer than Evian, crystal clear, no stains, no calcification and a happy wife. Itís also perfect for electrolysis.
Total cost for this was $5,600 but Iíd have installed that anyway as weíll recoup the savings on more efficient laundry and dishwashers as well as much longer life for those and other appliances. Iím also finally able to wash the Teslas at home without leaving hard water spots all over them.
Having improved the water quality 1000%, Iím installing a second solar water heater this week which will provide hot water to the kitchen and laundry room.
As we were planning the construction of our new stables, the architect asked what the elevation should be and it occurred to me that we had an opportunity to site it perfectly for maximum power generation for a PV system. I brought in a solar expert to look at the location and weíve chosen an ideal spot, close to the existing barn and well away from trees.
Working with the architect we increased the pitch of the roof slightly and sized the rafters to be 2Ēx8Ē with 48Ē spacing to make it ideal for the PV install. Being able to specify things down to fine detail will also make later installs cheaper and faster.
All permits are now in and we expect to break ground in about 10-14 days. Itís masonry construction so preparation and the foundation will take two weeks, the walls another two and then two weeks for the roof. Once the roof is up, PV installation can commence, even while interior finishing and fitting takes place.
Solar PV Panels
Having reviewed available products, weíre almost certainly going with AXITEC 60 cell, polycrystalline modules. These German panels have a 12 year manufacturerís warranty, guaranteed positive power tolerance and incredibly strong frames (this is hurricane country after all). They also guarantee 90% of the nominal performance for 15 years and 85% for 25 years on a linear scale.
The final size of the system will likely depend on exactly what rebates we can get our hands on in the FPL lottery but there will be an option to add more later if needed to support the hydrogen fuel cell concept.
I mentioned earlier than technology has moved on since our previous install and we also have more space now. With a large barn/shop and a generous two car garage thereís plenty of room to locate a couple of large inverters.
This definitely means a cheaper system/install over the micro-inverters but with the latest technological developments I will still be able to track and monitor system and module performance.
Iíll blog more on the details of the PV Modules and the Inverters as we move forward. Costs for both are being worked on as I write, but Iím expecting something around the $100k level in total with around $70,000 in rebates. Iíll also write up a more detailed post on the total finances as it all starts to pan out.
Florida is still a patchwork of small vendors when it comes to PV systems, no SolarCity here, so weíre likely to be using RegionSolar based in Sarasota which also happens to be owned and run by a personal friend.
This is going to be a feature of follow-up blogs. Discussions are still preliminary but promising. The technology is there and the whole concept is feasible. One of the best examples is Verde LLC in Braintree, MA. However, we're also looking at Ballard, Horizon and ClearEdge.
We have a few issues still to figure out with regard to load spikes e.g. when AC systems start up, and what options we have in managing load requirements for charging the cars.
Watch this space....
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