Thread: Solar power

Originally Posted by 1976_michelle

Just that lpg needed to be a particular percentage lower in cost than petrol given the reduction in miles you can get on it per litre for it to justify the cost of the conversion, and with the gap between lpg and petrol prices closing the worth of it is not so great (though I'm sure still there, just take longer to cover itself)

In the case of power, what has been raised with the connection costs and usage costs rising is about what I would expect
Right about now we'll be wishing the government never sold the power companies... perhaps it's time they take them back

I think you have things a bit twisted there... The economics of solar are completely different to LPG. Even with no feed-in tarrif, a large solar system will pay for itself eventually as long as the admin fees from the power company are less than what you would be paying to buy the power from them.

In most cases power prices are rising because the companies which own the infrastructure have realised that they haven't been upggrading the infrastructre at the right rate.

If the power retailers start charging too much in admin fees, those with solar can switch to a stand-alone (battery storage) system.

Originally Posted by Mr Whippy

I have discussed this with solar installers and have been told this can have problems. Apparently the panels are set up in groups run in series to supply a much higher voltage than the 12 volts(or 21volts if you are talking about unregulated volts)

Now I do not know if this is correct but I was told that if you add more panels they must be exactly the same as the existing ones. If you can no longer buy them you cannot add any more.

Would be interested to hear from anyone that does know about this stuff, as to whether this is correct.

Solar panels are set up in strings, that is connected in series. The limitation of how many can be connected in a string is usually the maximum string voltage the inverter can handle. More strings can be added in parallel to the first string but to work efficiently their characteristics must be similar to the original string, you can't just use any panels.

Each string or group of strings is managed by a MPPT controller. This is a Maximum Power Point Tracking controller which ensures that the panels are managed to give maximum power for the prevailing conditions.

Solar inverters can have 1, 2 or 3 MPPT controllers. These controllers work independently of each other to achieve optimum power for each input so it doesn't matter (as long as you stay within design parameters) what mixture of panels you have between controllers as long as the panel characterists are the same for each controller.

One method if you were going to set up an upgradeable system would be to use a multiple MPPT inverter and set up the original panels on one MPPT leaving its other MPPT controller(s) for expansion.

Inverters can be connected in parallel. So another method is to just buy an inverter with capacity enough for the original panels and when upgrading buy another inverter and parallel its output with the original one.

With panels on different azimuths (roofs pointing in different directions) you must have a different MPPT controller for each group.

Hope this helps

Deano