The Mudcat Café TM
Thread #97048   Message #1909722
Posted By: Rowan
14-Dec-06 - 05:15 PM
Thread Name: Should we install Solar Power?
Subject: RE: Should we install Solar Power?
Donuel
Things may have changed a bit but, when I was buidling my house and calculating costings, the total cost of connecting to the grid was $12k (these are Australian dollars) while installing photovoltaics sufficient to run an efficient (read "careful") household was $20k; subsidies only started once the cost exceeded $20k. While there was some ongoing cost regarding the panels the major such cost was maintenance and replacement of the special batteries, which had a 10 year life expectancy. So we went onto the grid.

As a person who'd lived (and run school camps) well away from the grid I was prepared for the constant 'situational awareness', both technically and temperamentally, required when you live where you need to cope with monitoring electrical supply, water supply etc. But my then partner had quite different strengths and found it difficult to come to terms with the relatively simple (to me) monitoring of the water level in the tank that collected from the roof and using the transfer pump (a 'firefighter' model) to transfer water to the storage/header tank up the hill.

I mention this because many photovoltaic systems require 'situational awareness' and consequent behaviour modification (not using the washing machine when you want to watch the telly is a minor example) and many people find it difficult to cope with the constant need to "think" about things that most of us take for granted. The best example for me was the behaviour of city people at the school camp I ran. Water only existed in the 9" between the tap and the plughole until they came to Steiglitz, where they found that water to make coffee and wash up in either came with wrigglers (mosquito larvae ) from the tanks of roof water or sediment (clay suspension) from the dam; if they didn't wait for the toilet cisterns to fill completely before flushing there wouldn't be enough flow to prevent them from becoming intimately familiar with the operations of a septic system.

All good fun and a great way of educating people about how we all should monitor the effects of our behaviour, constantly. But some find it a grind they want to leave behind them.

Jim Martin
You may well be right and it may well be that the electricity suppliers are using such argument as a way of dragging the chain; I don't know. For a while I lived a bit further west of where I now live and was in the very last house at the end of the last spur of the local power grid. If three people closer to the grid all turned on their kettles at the same time my power supply would cut out. At least, that was my hypothesis for the frequent morning power cuts and it got worse during shearing. Most domestic power supplies in Australia are 'split' into two, with electric hot water services connected (and metered) separately during "off peak" times in the wee small hours. The off peak connection at that house was switched by a 'clock' timer in the meter box and, because of the frequent power cuts was routinely delivering "off peak" power at times when there was peak load on the grid.

This was later fixed by replacing the clock timer with a pulse switcher; an HF pulse would be sent down the grid power lines to connect and disconnect the "off peak" domestic circuits. It struck me that distributed domestic power generators could be controlled by a similar mechanism, the theory being that domestic photovoltaics and turbines are connected to the grid by an isolating switch that only remains in the "connect" position while it receives an HF signal down the grid lines; when this signal drops out the isolating switch trips the generator out of the grid.

All photovoltaics generate DC (which needs to be inverted into AC) and turbines (the old Dunlites were DC but these days I suspect everything is AC) would all need their power 'conditioned' at the house before it's delivered into the grid so I suspect such an isolation mechanism could be part of the black box that does the conditioning. Should be a doddle!

Beachcomber
As they say in the classics, all power to your elbow!

Cheers, Rowan