"Hybrid Generator"

The following Blinding Flash of the Obvious is a huge marketing opportunity for someone.

Typical emergency generators tend to have a voracious appetite for fuel because the run full speed even at low load. The Honda "inverter" generators can throttle back at low load but keep running.

Why not take it a step further and add a built-in battery and auto starter to an inverter generator? Now you have continuous "keep alive" power to your heating system, refrigerator and lighting circuits, and the engine kicks in when the load increases.

I would think that the appliance amp draw upon start up would be a problem for consumer class generators.

For example, when a fridge or freezer compressor kicks in, the amp draw is many times higher then once running. For this to auto start the generator, the battery at the generator would need a 12 volt inverter to briefly handle the appliance start load until the generator started and came up to speed.

The main problem here is the size and weight of the battery and the added cost. Most small 2KVA inverter portable generators are weighing in at around 25Kg dry. Adding a 1Kwhr battery capacity using an SLA battery will take the weight of the hybrid to nearly 100Kg. Suddenly these generators aren't portable anymore. Going to LiFeYPo4 battery will take the weight to around 45kg.

The cost of ownership would also more than double to take efficiency from 20% to 40%. i.e. Hybrid generators would unlikely to cost less than $2000. A better solution would be to have a portable solar powered battery/inverter system module which can be boosted/recharged very quickly when required via mains or generator when required.

Having an electric start like the Yamaha gennies combined with an integrated control signal to boost/recharge the solar battery module when required would be a better solution.

You could then have the choice of purchasing the solar/battery module as an additional module for the Generator to turn it into a hybrid.

That's the point. A standard lead-acid starting-duty/marine battery would probably be optimum. The inverter already has to handle the startup current draw of the load. In a few seconds once load has settled down, the engine could start up. For lower loads, the system would run off the battery for a while.

Incremental cost is the battery ($100) and starter motor ($50?).

What you are talking about is kind of like how an off-the-grid system works.

A buddy of mine has solar panels on his home, which charge a bank of batteries. The batteries than feed an inverter, which runs his house. In case the battery voltage drops too low, a stand-by propane/natural gas generator kicks on to charge the batteries and help power the home.


It's a great system, as he's completely independent of the power grid. He also bought a Chevy Volt for his daily driver, so now for most short trips he doesn't pay for gas either.

It has two major downsides though. The first is cost, his system was tens of thousands of dollars to set up. The second is the amount of space you need. Between the propane tank, generator, solar panels, battery bank, inverters and controllers it's definitely not a portable system.

You could probably make a portable size version, but it would put out a very low wattage for its size and weight. It would also likely be very expensive for the wattage.

I was going to build a diesel single cylinder Yanmar motor running a Tractor Trailer alternator to idle along and charge a battery bank. Thne run an inverter. This would NOT power large high amp things but certainly could run lots of LED lights and some simple things. Quiet and fuel efficient. This was mostly for a homemade RV thing, but could work just the same for bugging in.

Ironwood

since the demand for a refrigerator compressor start is triggered by a thermostat, how about a time delay relay, that can first energize the electric start of the generator...allow a 15 or so second run time to get up to speed... then energize the relay to start the compressor....when the compressor kicks off, it grounds the ignition to stop the generator....

comments from engineers?

With some generators, at least, the recommendation is to run them for two minutes before putting on any loads.

I'd probably go for a propane powered fridge. Or I'd figure out how often I needed to run my generator to keep my fridge and freezer working, and just run it that often.

I've been on the lookout for a full size propane ammonia absorption refrigerator for a lot of years...we have several stilt homes about 1/2 mile off shore in the Gulf.. off the mouth of a local river... in the early days (50s and 60s) they all had ARKLA refrigerators and Aladdin lamps before generators were popular...

you could dial in any time delay on the relay

The new refrigerators are very efficient and run easily with a small solar system,then back that up with a small genny.Also the surge power for startup on new appliances is far less than older models,we have come a long way last ten years on appliance efficiency.

You dont need the hyper epensive bleeding edge solar models now as solar costs have gone through the floor they just dont pay.EnergyStar standards have come a long way for regular consumer models with little added costs.

Solar has the advantage of sustainability longer term after propane long gone.And pretty much youve paid upfront for the energy costs.

When Bud went with a solar powered freezer he went three years and never needed to run his genny at all to back it up,running his home on 800 watts of solar.This was Northern cal on a mtn with snowy/rainy weather.

The one that failed was his propane refer,the pilot blew out and he came back to a rotten mess,he would leave a month at a time.

Remember,when your solar is producing less during winter r/t bad weather/less solar gain your cooling needs are also reduced at the same time.

His freezer was on the back porch (you could put em in an unheated room),lower ambient temp less temp differential you need to overcome.

Solar is the way to go for refer/freezer needs,really works well.

Les,a good source for propane refer are old RV's.And the older models are better quality.Ones from the 1970's will outast you,getting 10 years today is pretty impressive say many folks.

However,total energy used puts propane at the top of the list vrs electric.Used to have the numbers,but propane fridge uses about 4 times the energy a modern 'EnergyStar' refer uses IIRC.They are NOT energy efficient.

Those old RV fridges are very finicky though. They only cool to about 30 degrees below outside temperature so in the hot summer they may not keep your food/medicine cold enough.
They also have to be kept level, if I take my camper out of the garage to the driveway the fridge warms up.

Eugene,true to a point,in the RV on the road they bounce around so level less important.

Our 1979 3 way refer would freeze still in 100 + weather but that was on electric,you are right,less cooling on propane but I dont recall ours ever getting warm on propane,just wouldnt freeze things very well.

On 12 volt its use was pretty marginal for sure.It certainly had limits,very good point.Thanks for pointing that out.

Some work arounds are keep direct sunlight off backside and a computer fan over condensers helps too.

Friends indoor old Serval type was a fine machine just on propane.They are fine machines that last forever but.....

Im much more impressed with electric models,they are better appliances overall in offgrid/grid down scenarios IMO.

But I wont knock anyone getting propane,they work and work well no doubt about it.Just breaks down to how it will be used for YOUR particular needs as you percieve them,thats variable and the right answer is what works for you.

That is similar to what I did for friends.
The fridge thermostat calling for cooling automaticly energised the remote start control of the generator.
When the fride was cold enough, the generator stopped.
This worked fine for several prolonged power cuts.
The freezer was also connected to the generator, but had no automatic starting provision, it being considered that simply running the FREEZER whenever the FRIDGE called for power would be sufficient.
Whenever the generator was running it also supplied a 1KW water heater and a large battery charger. Lighting was 12 volts from batteries.