Power Dispatch

Not knowing which part of the world your on makes it difficult to provide a reasonable answer, albeit a hypothetical one.

My immediate questions are;

Why would you not spec a generator to cope with all the prospective demand?

If you have access to grid power, why throw money away running a generator? The cost of fuel would be greater than the tariff charged for mains grid power.

There are systems available utilising PV solar panels and batteries. Where the excess capacity of the PV panels is fed to the grid and the power company pays a rebate for that power. It is only economically viable if you discount the initial cost of the system. PV panels don't "cost" anything to run per se, but you are restricted in the amount of time during the day when they can supply generating power.

With a diesel generator you have running costs and maintenance costs to factor in. Even if you run it on WVO or Bio diesel it still will cost more than grid power.

I have visited many places where they have generating plants in the facility.

Where the mains supply is of poor reliability, many organisations will run with synchronised generation capability so their machines don't stop.

For instance, a 3 second power outage on an injection moulding machine or electronics surface mount machine can initiate a full manufacturer's diagnostic restart that takes up to 35 minutes before return to normal operations. One factory I visited averaged 5 such interruptions per shift.

We in Aus are indeed very fortunate to have such reliable electricity supply.

I know this post says it's for a house, but maybe they are searching for information to bridge their knowledge gap.

You are correct to mention that there are system controllers (similar to those used for PV and windmills) that can manage the load sharing between on site generation and external supply. Whoever was able to provide the synchronisation capability for their generator would also have the ability to implement load sharing for them.

There has also been another thread opened for a "very economical electrical design for a house". Maybe this is linked. (Both have initiated from "Guest" posts.)

Another couple of things to consider,

If you are in a Urban/Suburban situation, then running a diesel generator for any length of time will get you in trouble with neighbours, EPA, and local councils due to the noise and fumes of the exhaust.

You may also fall foul of local ordenances with regards storage of fuel. You will need to store quite a bit in order to run your generator 24/7. All it takes is for one neighbour to get narky about the noise and your experiment is finished.

Same goes for backyard windmills unless the blades are tuned to be quiet.

Of course you could also find your local power supplier may not want to be a party to this either.

I have also been involved in "Critical Operation" sites where the mains grid power was backed up by UPS and Diesel Generators and I don't mean little 5kva jobs either. The UPS carried the load irrespective of whether the mains power was available or not. When the Mains dropped for more than a nominal time it kicked in the 80kva genset. Fun costs money how hard do you want to laugh...

You are quite right in that Australia (in general) has very reliable mains power.

The way I read the Guest OP question was that he wanted to run a diesel generator of nominal capacity, 24/7 and when the electricity demand in his house peaked above the generators capacity then he'd bleed in the mains grid power to cover the shortfall. For most "western" domestic power requirements a generator of 12kva is more than sufficient and it has capacity to spare. Hence the question if your going to buy a genset why not buy one that'll do the job?

If his house was in a remote location I could sort of understand it but in most Urban/Suburban situations I could not see any net benefit.

I suspect the other post is related to this one. Perhaps the Guest OP didn't like my answers..

Sorry, Nope, this is the first time I have posted to this forum.

Firstly, this is to cover a knowledge gap (thus the hypothetical part). Secondly, In regards to the location, consider the cost of fuel (running a gas generator set at 20kva) to actually be cheaper then mains power as I live in a developing country and we face loadshedding for approximately 8 hours a day. Thirdly, that is our usual load, however, at certain parts of the month we may peak to 60-80kva (when there is mains power to boot).

Dear guest, your house power usage at 20kVa seems extremely generous in power usage. Even with an electric hot water system, electric stove and many other "mod cons" our usage is less than 20kWh per day.

Please re-visit your power usage and confirm the total power you expect to be using. 20kVA would mean that you use 480kWh of energy per day in your "house". That power level is absurd/does not make sense and thus I suspect that somewhere your calculations have gone astray.

You should consider the language usage difference in a "developping country".

a house could mean any building and a house in a " developing country" may have 10 families living there so a 20KVA consumption is realistic.

Dear Guest. If you synchronise a 20KVA generator to a grid it will cost you more than the price of the generator it self.

You need a synchronising module with load management system. I can sugest DEIF AGC3 or ComAp or EasyGen3000

All they can do the Job you want but will cost you as much as the price of a 20KVA generator

You would need some isolation device from the grid when it is down to prevent feeding power to the neighborhood and potentially harming maintenance crew expecting a dead line.

A parallel generator must be synchronized with the line and must be registered with the utility as it could affect the protections and stability of the distribution network.

In general, one disconnects from the line when running on emergency generators. On line installation must be done with the greatest care.

One possible solution is to run the critical equipment on an independent plant distribution circuit isolated from the utility. Non-essential loads being feed by the utility. But this might not be easy to do either.

You will need complete power system for the purpose apart from permission from the your main power supplier. You would need not only synchronizer, but also switchgear, isolators and protection system so that in case of any fault in your system grid does not feed the fault. All these requirement and safety of the system (when your section of grid is isolated for maintenance, your system should also get isolated from grid) would make your system non viable

Hi, As I said, This is more hypothetical in the case of the technologies that one would use if applied to a larger setting.

And 20kva is pretty much regular down here for a family of five in a medium-sized house. Think 4 2-ton A/C systems plus about 3 refridgerators/freezers and a load of TVs and Lights. We have seen loads spike to about 60kva when the whole house is "on".