Solar Panels and a Sefton Heat Engine. Need inverter recommendations.

I bought a heat engine, and would like to hook it up to my electrical panel.  It should max out at under 1.4KW.  I know I'll need an inverter.  However, I have to call my local utility and get the job approved.  I could theoretically run the heat engine on fossil fuels, so I don't even want to try it.  Instead, I want to get a couple of solar panels (under 1KW total) for the purpose of getting approved.  It was recommended to me to use separate inverters in order to keep things simple.  I haven't looked into trying to make it work with one.

I still live in a city, and don't have a lot of woody biomass available, so this is more for testing purposes.  I don't want to invest a lot in this property, where I won't be living.  That said, I can imagine getting a battery backup system might simplify things.  E.g. I've seen backup systems with built in inverters, and I could use an alternator to charge the battery, but that would probably involve some modifications.  I wanted to get some feedback from the forum, since my setup is somewhat unique.  I tried searching around for people using hydro and solar, or solar and wind, etc, but it occurs to me that none of those exactly match my situation, so I was hoping to jet get some general pointers to get me headed in the right direction.

Thanks.

Hi Brian;  Welcome to Permies!

Tell us more about your heat engine.  Photo's ?

So, your wanting to use solar panels to generate electric heat. That heat will be used to heat up your heat engine … to make power ?  Have I got that rite?
If I read your numbers correctly, your hoping for a .5 kw output? That's not very much.
But if it allows you to learn about your engine. Then when you do move out of town to your own property , you will be an experianced heat engine opperator.

Is the idea to use a heat engine to drive an electrical generator? If yes, you could use an induction motor to couple directly with the grid. Induction motors are really clever that way. Automatic uncoupling from the grid if grid power is unavailable.

A heat engine operates on heat, not on electricity. The return on investment isn't good to convert 20% of sunlight to electricity, and then convert it back to heat to run a heat engine. Better to convert sunlight directly to heat, which is something like 90% efficient. Then use that heat to drive the heat engine, which drives a generator.

thomas rubino wrote:Hi Brian;  Welcome to Permies!

Tell us more about your heat engine.  Photo's ?

So, your wanting to use solar panels to generate electric heat. That heat will be used to heat up your heat engine … to make power ?  Have I got that rite?
If I read your numbers correctly, your hoping for a .5 kw output? That's not very much.
But if it allows you to learn about your engine. Then when you do move out of town to your own property , you will be an experianced heat engine opperator.

The heat engine comes from Sefton Motors, which is a shop that just got out of the owner's garage.  He has some videos on youtube.  I've been speaking with the guy, and I get the impression that he's an honest broker, so I decided to take a shot on it.  I like Stirlings, I've built some toys, so I'm probably in the niche market for this thing.

As to the application:  I plan to run the engine on wood and such (dried grass clippings, bark, etc;  just bought the RMS book).  I need to get solar panels only so that the public utility will let me tie in to the grid, and would just be regular PVs.  I doubt they will approve it just for the engine, since it is not per se a renewable source of energy.  Even if I run the engine straight into a battery, I'm fairly sure this approval would be necessary, unless I'm going to physically switch the circuits on and off grid, which would not be practical, especially at 1.2 KW.

If I get 1.2 from the engine and 600 KW of panels, that would put me under 2KW.  

Joseph Lofthouse wrote:
Is the idea to use a heat engine to drive an electrical generator? If yes, you could use an induction motor to couple directly with the grid. Induction motors are really clever that way. Automatic uncoupling from the grid if grid power is unavailable.

A heat engine operates on heat, not on electricity. The return on investment isn't good to convert 20% of sunlight to electricity, and then convert it back to heat to run a heat engine. Better to convert sunlight directly to heat, which is something like 90% efficient. Then use that heat to drive the heat engine, which drives a generator.

Yes, there is a generator.

Is an induction motor different enough from an inverter that I can install it without notifying the utility?  They do everything they can not to buy renewable energy from the clients, so I wouldn't feel bad not telling them.  I could skip on the panels if it's possible.  I plan on moving, and this is more a test platform.

I edited my OP as it's unclear.  The PVs are just to get myself tied into the grid.  The tie in needs to be approved by the power company.  I doubt they will approve it for a heat engine.  They will say they have no way of knowing if they are buying renewable credits.  Maybe I'll run it on waste motor oil (I won't).

I plan on running the engine on woody biomass.  That said, the guy is designing a solar collector which will have a PV and reflective layer, depending on wavelength, the latter being similar to how some windows work to let light in but keep heat out.  I haven't done the math, but at 20% efficiency, that might come out to 4 or 5 m^2 to run the engine, but you'd theoretically get whatever PV efficiency is these days on top.

Brian;  That Sefton engine is a very cool looking/sounding unit! The price is even good.  I'll be looking them up on u tube later.  

We / I, definitely would like you to document your  experiments with it.  
You are correct about the utility company. They are only required to purchase renewable energy. Solar or wind only.  No hydro... apparently water is not renewable... pay no attention to that wet stuff falling from the sky...
I'm 100% off grid ( solar hydro)  so having never done a grid intertie system, i'm not sure of the eqipment requirements.
I can tell you that any inverter you buy should be a pure sine wave design.  I would shy away from the cheaper china imports.
When you are at a place to want batterys then be sure to buy the largest / best you can afford.

Again, please keep us posted on your Sefton!

A hybrid inverter or battery based inverter with back up will interface with the grid in a number of ways. You need not get an intertie if you want to use the heat engine on the generator input of the inverter/charger. Then the system would use solar energy to augment the system, allowing solar priority to loads and backfeed if you like, with itility approval.

An outback vfxr in any wattage/voltage combination or a radian 4048 is a nice machine for the application and the software/hardware can and will do. Program-ability of all these parameters, as load control, diversion, grid and or generator connection setpoints, etc., is essential to operation flexibility.

The machine can be run entirely offgrid or only pull from the grid to satisfy loads..... nifty trick!

Offgrid or grid as backup and in bulk charge mode, the system would simulate a grid tie when the heat engine is operating as generator. Also the system would totally backfeed the output of anything feeding the battery or inverter, if set up correctly. This requires full disclosure with the utility.

There is a point where you may need two inverters (ac coupled) but not if you use a charger capable of taking the output of the generator and feeding it to the battery.

A dc generator is the best scenario for a backfeed of that output, i think. I need to look see, what could work.... an inverter section from a fuel engine generator, maybe.

Sma has better ac coupling and generator parameters. If you use sma, get all the comms in order......

The heat engine is a great charger, i looked after commenting. One inverter would do, 12v or 24v. Not sure about charge control, and the temp differential requirements. A 24v vfxr2400w-3500w inverter with a mate3s and flexnet on 3 shunts would getter done. Likely a flexmax charge control can handle the heat engine.

frank li wrote:The heat engine is a great charger, i looked after commenting. One inverter would do, 12v or 24v. Not sure about charge control, and the temp differential requirements. A 24v vfxr2400w-3500w inverter with a mate3s and flexnet on 3 shunts would getter done. Likely a flexmax charge control can handle the heat engine.

frank, thanks for the responses.  

frank li wrote:
The machine can be run entirely offgrid or only pull from the grid to satisfy loads..... nifty trick!

If I'm understanding, it can function like a large/smarter uninterruptable power supply from the tech sector.  The good ones run the devices off the battery and use line power to charge the battery.  

Appreciate the feedback!  This site is great.

thomas rubino wrote:Brian;  That Sefton engine is a very cool looking/sounding unit! The price is even good.  I'll be looking them up on youtube later.  

We / I, definitely would like you to document your  experiments with it.  
You are correct about the utility company. They are only required to purchase renewable energy. Solar or wind only.  No hydro... apparently water is not renewable... pay no attention to that wet stuff falling from the sky...

since we're talking about the the utility, my research has led me to realize there are also some valid safety concerns for their employees with respect to backfeeding the grid, which is also why they want to get involved in the process.  Having said that, in some states they don't accept biomass.  It's pretty clear that they're not in the business of buying power.

thomas, I'll be sure to keep you guys posted.

Brian Church wrote:

frank li wrote:The heat engine is a great charger, i looked after commenting. One inverter would do, 12v or 24v. Not sure about charge control, and the temp differential requirements. A 24v vfxr2400w-3500w inverter with a mate3s and flexnet on 3 shunts would getter done. Likely a flexmax charge control can handle the heat engine.

frank, thanks for the responses.  

frank li wrote:
The machine can be run entirely offgrid or only pull from the grid to satisfy loads..... nifty trick!

If I'm understanding, it can function like a large/smarter uninterruptable power supply from the tech sector.  The good ones run the devices off the battery and use line power to charge the battery.  

Appreciate the feedback!  This site is great.

It will backfeed any power not usable onsite and transfer back and forth from grid to backup more or less seamlessly, your computer wont crash or anything, but you may just detect it, depending on lighting.

It will also attempt to use solar to power loads directly and overnight from storage in order to use max solar power and sip from the grid, no backfeed. Totally programmable.