Ticking all the boxes

[creeky]

I was going to send this link to the gf. But after seeing that structure. I'm afraid to. I echo Marcus' remark. Great work.

[randen]

The next facet for the solar pergola has been tested. The inverter was wired temporarily and provided 220 VAC to a 5hp motor. Now it was under no load but ran smoothly drawing just a couple amps.

The goal is to provide power to the home (for summer loads so far) and of coarse the largest load is the heat-pump for the AC.

Now here is the problem: I know some are going to respond "why don't you grid tie" NOT ALLOWED. The grid that services our home is already loaded with as much solar as they will allow????? I have applied 3 times. Safety "they say" I smell B.S.

Here is my plan: Have the Nimh pack out of my truck which is 29 kwh's or once was. I will keep this charged from the solar and invert to supply the house loads. I will install a transfer switch so as long as the batteries and solar are providing for the load the grid will be disconnected. If clouds happen and the batteries are exhausted the grid will turn on. Simple Eh.

I will provide some photos as the project comes together.

Randen

[MN Renovator]

Have you found an out of the box transfer switch that will do that automatically?

[randen]

MN Renovator

I have not found any out of the box transfer switch. Any of the big name inverter manufactures are still stuck in the dark ages of producing products meant for lead acid. Some inverters and charge controllers coming out of China are being made with high voltage lithium packs.

I would like to obtain a couple of Tesla Powerwalls. These are exactly what I need. They can be programmed to do either grid tie or islanding smoothly. I had called Tesla and they told me I wouldn't see one until at the earliest early 2018 for my area. Damm.!

But who knows by the time I can get everything together the Powerwall may be available.

I though I was going to have the pergola up last year. Need a bigger gun for all those gremlins that show up!!!

Soon I will be running the conduit up the exterior wall and over to the already installed conduit to the panel area. It been 20 year since I built the house. I had included a conduit from the roof down inside the wall for the eventual installation of roof top solar. Again didn't think it would take this long. The solar cabling has arrived in my post box. Very soon the batteries will be drinking up some solar.
electrons.

Randen

[Fordguy64]

I didn't see what batter voltage you are wanting to run. But magnum inverters have a new thing now. The have micro inverters at the panels that back feed into a battery back up inverter. The inverter its self is the charge controller and it has a built in transfer switch for grid or generator.

An article I found that kind of explains it
http://www.solarpowerworldonline.com...erter-battery/

[MN Renovator]

For my own personal theoretical on-a-bar-napkin design involves a very simple charge controller, because lithium is dead simple needs very little control with low C rate inputs when charging. If you keep the voltage within the safe range and the maximum charging rate isn't too high, a lithium iron phosphate pack(LiFePO4) can pretty much be provided power until the cutoff voltage is reached.

This is very different from lead acid, which is finnicky, where you have different charging regimes with a bulk phase with limited current until you reach a certain voltage, then a float phase where you hold a specific voltage for a certain amount of time, and then periodically you need to do an equalization phase, which mostly wastes energy and wears the cells down cleaning sulphates off the plates while eroding the plates, on top of the charging inefficiency that already exists with lead acid cells in the first place.

With that being said, I'd have a simple charging and discharging system that uses a relay to disconnect the pack when it is out of range with solar modules that have an appropriate voltage that fits closely with its MPPT to the primary portion of the charging curve of the battery. The system can be simple and the savings in the charging system can be used with additional solar modules which should more than make up for the additional cost from the near-monopoly that exists in spendy lithium charge controls.

For an islanded system that isn't grid tied but the grid is available, you'd size the solar system so it provides your intended loads for about 9 months out of the year. In the winter in snowy regions like mine, the solar system would probably cover the fridge load and maybe a little bit of lighting and/or the furnace on the days with sun. Cloudy days, you're on battery or grid. My personal goal would be to have enough solar to run a 500 watt air conditioner(or if you don't think your inverter will blow an inverter mini-split that would be even better) with full sun in the summer with enough solar overhead and battery to carry the small air conditioner through a number of hours into the night along with the refrigerator with the goal that the battery is nearly drained by morning. The hottest days inside the house are always the days with full sun and the solar gain involved. In my area in MN 1kw of nameplate of my grid-tied solar system on a hot sun days without clouds produces about 6kwh of energy. Adjust nameplate wattage for your desires and round up a little. Have a battery sized to support the maximum discharge load, charge load, design capacity, and then oversize a little figuring degradation and the different between the granular size of the batteries.

..at least that's my idea for an on-grid system, pole mounted in a spot with a clear view of the sky. In my case, most of the expectation is for air conditioning and I'd be inclined to get more of the available production into the evening to match the needs of the air conditioning load.

So basically what I'd want is a system that sees that the 120v from the 48v inverter is absent because the system shut down due to the battery hitting my low voltage threshold and the air conditioning, fridge, and whatever other loads I've dedicated to the system automatically make a break-delay-reconnect to the grid.

EDIT: If I were to get an electric car or a PHEV, I'd size the solar and battery system a little bit bigger. The reality is that I wouldn't want to oversize the system too much because the more idle time without a load to dump into, that would be less I'd get from the system. I'd also consider using some of these super cheap used EV batteries that I've seen floating all over the place. ..although that gets tricky because getting into the right voltage range for an inverter requires either planning the battery around the inverter, or the inverter around the battery. Especially in packs that are hard to change their nominal voltage, like Tesla packs, you can't really rearrange the cells to get the ideal number you want in series. It's a little easier with Nissan Leaf cells or similar packs where your granularity is 2 cells in series.

[randen]

For the moment I'm going to use the 360V pack that was in my truck. It was rated at 29 kwh which should power the house for more than a day with the heat-pump. My experiment with the inverter went very well and I'll post more when its up and running.

The cabling has arrived and I'm watching for the combiner box. Still looking for the charge controller. It seems a automatic transfer switch for the size I need is quite pricey. Looking at my options. I didn't sell my toolbox yet.

Randen

[jeff5may]

With the mandatory off-grid situation you describe, you may be better off just running everything off of your inverter full time. When the solar goes away (nightly or heavy cloud cover, etc.), the battery bank could be run down to a certain point. Below this threshold, you could just energize a grid-powered battery charger to keep the battery bank alive until the sun comes up again.

I know this isn't the most efficient way to run your loads, but it's a whole lot easier and cheaper than a custom-islanding transfer rig. It would essentially work as a UPS, so sensitive loads wouldn't be getting glitched or seeing surges and spikes when contacts made and broke. Extending the lives of equipment could very well make up for the conversion losses. A lot depends on the kinds of loads on the power line that would be exposed to the transfer switch. This is one of those cases where trying something strange and new might not be a very good idea.

[randen]

Fellow Eco-renovators

Boxes have been arriving with combiners with disconnects and solar wire with MC4 connectors. Spent a whole day up and down the ladder installing conduit and wire. The disconnect is the next order of business.

Getting close however the charge controller is a little special so its going to take some time getting here. It looks now like its going to be another 4 weeks before I can direct some electrons via photons to the EV's

Randen

[antdun]

I love it! I sent some of your pictures to my wife and she loves it too. Hopefully we can do something like this in a couple years. Was the stainless steel quite expensive, or was it comparable to using other metals?