Solar Choice
Plenty of Australian homeowners dream about going off the grid with solar panels and home battery storage. But for the average, grid-connected Aussie home – which consumes between 20 and 30 kilowatt-hours (kWh) of energy per day – installing a system large enough to keep the lights (and everything else) on throughout the year just isn’t worth it.
If they rely solely on solar and batteries, such a home would need enough capacity to carry them through 3-4 days of gloomy weather. Right away, this is a significant financial commitment, especially when compared to the relative affordability of grid-connected solar systems, whose prices sit at historic lows in Australia.
As a result, it can be difficult for a home to reduce its energy consumption dramatically without causing inconvenience or discomfort for at least one of the occupants (e.g. the one who keeps the electric hot water heater on its toes with their marathon showers). Another hurdle is occasional usage spikes – when multiple devices (vacuum, washing machine, dishwasher) are all turned on at once. While the grid can handle such events with ease, a home relying on batteries and solar could quite easily trip the switch unless the system has been specifically designed for these occasions (which a good system should be).
So in summary, for those who just want to go about their daily lives without thinking too much about how they are using energy throughout the day, completely disconnecting from the grid may not be particularly appealing. Installing a partial off-grid system might be a good option instead.
For most homes, electricity usage patterns for certain things is completely regular and predictable. Refrigerators, lighting and chargers for smartphones & laptops, for example, all consume minimal amounts of electricity at a given time, making them ‘low risk’ devices to target for removal from a grid-connected electricity circuit. Imagine if you could use them 24/7 knowing that they’re running on your home-grown solar energy – making you largely independent of the grid, but also resting comfortably with grid access whenever you need it for the rest of your home. This is the promise of a partial off-grid solar system.
The main benefits of a partial off-grid solar-plus-storage setup are:
The main disadvantages of a partial off-grid system:
Source: SolarChoice. Reproduced with permission.
This post was published on December 7, 2016 10:59 am
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I've been considering doing this for a while but am concerned I would lose my SA premium FiT Due to expire 2028.
I export most of my power so it is pretty important I keep that. $;-)
I've also read there is a minimum energy use regulation? 400KWh per year?
Rod, the way in which I've configured mine is in the form of an emergency backup system. This should not trigger any problems with any distribution authority as all you are doing is providing your own backup in case of network failures. The key as outlined in the article is to configure your circuits into services i.e. lighting, refrigeration, cooking, communications, general GPO, space cooling/heating etc. Once you have smartly configured your circuits with a "services" focus you can divide them further into "essential" and "non essential". Essential services are usually low power and energy i.e. lighting, fridge, communications (router, modem NBN), fans etc.
I've used a mains change over contactor (operates within 1 mains cycle) with an mains inverter connected to the battery, the operating coil on the contactor connect to the inverter. The contactor coil could be connected to either the mains or inverter but will draw about 4 Watts continuous. The changeover is sufficiently fast that most appliances do not notice any disturbance. The inverter rating needs to be sufficient to start your fridge or any appliance with a high surge rating. My fridge while only drawing 150W in normal operation draws 12A for 10 seconds at the start of its compressor cycle so any battery and inverter system needs to be able to handle such surges.
The backup system must also not disable any of your RCD's (safety switches) and be upstream of them. Ideally replace your circuit breakers with RCD's they are cheep enough.
Thanks Ray,
I should have divulged my main motivation was to export more and import less = more $
Outages aren't a problem for us.
Any upgrade or alteration to my existing system would void the Premium SA FiT.
My main energy use is my fridge but, as you point out, a decent sized
battery/inverter is needed to cope with most fridge's start up.
A standalone system to take the fridge off grid doesn't make a lot of financial sense.
I spoke to a guy who is up with the SA regulations and although I could
have a ring fenced off grid system, the fact that I would be taking less
than 400 kw/h from the grid per year might trigger a review of my PFiT
So, it looks like BAU until 2028 or until electricity and or supply charges exceed my income for my exported energy.
Electric vehicles with 30+kwhr batteries will essentially allow offgrid capability in conjunction with a modestly sized solar and stationary storage system.
Before you start. It presumes you can charge off site on the very odd occasion you need to and your stationary system covers approx 90% of daily circumstances.
I like my grid-tie limiter inverter, doesn't feedback power to grid and it's cheap (Chinese) I don't know why company has not UL certified it since it works so good. I guess there is one or two of the other more expensive inverters can be set to 'no sell' mode, not sure.
But anyway, I don't want to netmeter (though that is useful) because of all the stupid fees and permits needed. Plus some Utilities still requiring two meters, that is the stupidest and unwanted, because the Utilities are now forcing you to purchase all electric (along with everything kilowatt of distribution cost) you use, no matter how much solar you made and forced 'sell'. Instead of using your power first then sell if you making excess, with a one meter only, set up....It is cheaper if you simply use all that you make and only use grid if you have too.
It's all BS...But with my set up, it is simply plug and play, and no need to rewire home for secondary circuitry box...If I do have a power outage run extensions from 'off grid' inverter....
SOLAR ENERGY STORAGE
AND HOT WATER
Heating uses an annualised 60% of household energy in Sydney (Ausgrid data) and
a lot more than that in winter. A well insulated house would need to have
stored perhaps 20 or 30kWh of energy for central heating on a cold, cloudy
winter's day. This would be expensive storage if implemented using batteries at
more than $680 per kWh (the latest Powerwall battery cost without
installation).
To cope with several such days in succession, for instance during an East Coast
Low, figure on several times this amount so going off both the gas and
electricity grids in town doesn't make economic sense yet, particularly since
almost all houses would need more heating than this because they are so poorly
insulated. However there is a solution which radically reduces the overall cost
by reducing the amount of battery storage required.
The solution is to store energy for heating as heat. Hot water storage (45 to
90 Celsius operating range) can store 52 kWh per 1000 litres, water is cheap
($2 / 1000 litres) so most of the cost is the tank. This can be a cheap
unpressurised tank for hydronic heating or a normal mains pressure tank for the
domestic hot water service. The tank needs to be well insulated of course but
insulation is cheap. If the tank is mounted within the heated space then all
the tank heat loss goes to heat the space and none is wasted.
Hot water running through wall-mounted radiators is used all over the world for
central heating. A small pump is required to push the hot water around with
thermostats regulating the room temperature and there are no noises or drafts.
Hot water at 90 Celsius is too hot to use in wall mounted radiators so a
tempering valve mixes in cold water to reduce the temperature but this does not
involve any energy loss.
In summer, cooling rather then heating is required. Most cooling is required
during mid summer daytime, particularly in the afternoon, but solar panels are
producing their maximum output at this time so the solar panels can run air
conditioners directly, particularly if some panels are turned to face west to
provide power until sunset. Energy storage in the form of the house thermal
mass is free as the now cooled thermal mass will keep the house cool well into
the night.
Hot water energy storage systems are compact due to the very high heat capacity
of water, can be expanded in capacity for basically the cost of the extra tank
and store energy directly in the form that is most required in a heating
climate.
Batteries are still required to run your lighting and TV but such loads are a
tiny part of your power bill compared to heating. These days LED lighting, the
TV, fridge, microwave, induction cooktop and PC are all considerably more
efficient than their equivalents of 20 years ago.
Once installed, solar combined with energy storage as described, will fullfill
the old nuclear energy promise of "energy too cheap to meter".