Designing a Solar Roof - not as easy as you might think
If this "aside" post kicks off any longer discussion then I may ask to get it moved to its own thread, but in the meantime....
I had cause to do a couple of house designs recently, and obviously Solar Panels would be part of this. So that means that the roof needs to be designed to make the best use of things for a particular block of land.
This proved to be quite challenging, and with many things to consider.
Conventional wisdom says:
- Panels should be elevated to the same degree as your latitude. This is the best compromise angle. I say "Tosh" to this.
- Panels are best to be flat against the roof - this is cheaper than elevating them beyond the roof pitch. I say "Yes" to this.
- Panels should be North facing to make the most use of the available sun (in the southern hemi). I say "Maybe, but it depends..." to this.
Looking at point 2 first, this means that the roof pitch should be whatever the panels pitch should be.
Looking at point 3 next, (coz Point 1 could be lively :D) I would be inclined to put up about 50 panels if I could. The rebates are good and are about to start diminishing from Jan 18 at 1/14th per year for 14 years, and as a long term investment I think it is sound. Electric cars will be a thing of the future and when batteries are viable we will need significantly bigger batteries that they think we do now - especially depending on how far we drive each day. The reasons why I think 50 panels would be good are:
- It is a cold climate, so heating levels are increased (although proper insulation, design and passivity should help greatly with that)
- There would be someone at the premises virtually all day/every day so heating or air-con could be running a fair bit (esp heating)
- There would be a juice hungry bunch of machines in a large workshop :;. These also produce heat so air-con comes into play even more.
- Electric cars are coming - probably at about the same speed as decent affordable batteries
- Until batteries are viable (maybe 4-5 years) enough juice needs to be sent back into the grid during the day to largely offset the usage in the low/non elec production hours (and these are largely the peak usage hours). When batteries are hooked up the feed-in tariffs will just be more bonus for any excess power generated
- Having 50 panels means that some could be devoted to North-East and North-West presentation to make more elec earlier and later than with just North facing. This might account for 16 panels (8x NE, 8x NW). This of course depends on the specifics of the block and shading etc from other houses/hills/whatevers.
Noo then. Point 1, the elevation of the panels, which could provoke some discussion......I'll make that a separate post.
Daylight Saving DOES in fact fade the curtains more.....
....Oh alright so it doesn't BUT it does create more usable electricity for those without a battery. Think about it - the elec producing hours are shifted forward an hour, into the peak draw time. So you lose an hour in the morning when the draw is low but you get an extra hour in the late arvo when the draw is high.
How do outages occur .... and the meaning of life?
In response to earlier posts;
- About 80% of outages by time lost, occur at the 11kV level and therefore have nil to very little to do with generation. It is mostly to do with critical equipment failure even though the majority of Australian networks are designed to N-1 standard. 'N-1' means that any single piece of equipment can fail without causing an outage but if 2 pieces fail, then......? The second biggest outage mode is inadvertent damage such a vehicles hitting poles, accidental cable dig ups, animals and vandalism.
- Re outages due to lack of generation, (In NSW for example) by far the bulk of electricity is transmitted to the 3 distribution utilities by Transgrid, the transmission utility. Their Control room is constantly monitoring the input into their system from the generators and the output to the 3 utilities (plus (I think) 2 mega customers. If it looks like the required output is going to exceed the input, Transgrid advise the 3 utilities who will implement very well planned and rehearsed load shedding actions. IF THIS DIDNT HAPPEN, then the whole network can collapse, as happened in the North East USA about 20 years ago. The consequence of a complete collapse is horrendous and requires what is known as a 'black start' to get the network up again. A 'black start' is also planned and rehearsed but can obviously only be a virtual exercise. The problem is that you require electric power to start a generator and, if you don't have that power, then.....
- Back in the 'old days' there would have been less than a dozen inputs to the system (= generators) and that made the monitoring of the system as above fairly easy BUT there are now thousands of input points some of these are effected by no wind, others by no sunshine, flat seas, low water levels etc and so the constant matching of input to output is infinitely more complicated and hence has had to be automated. Don't forget that you have to exactly match input to output + losses. There is no such thing as surplus electricity or at least there isn't until storage becomes significant. That is the reason why storage is so essential to stabilise a network that has thousands of inputs and millions of outputs many of which vary by environmental and human factors that can't be controlled nor forecast by the network operators.
- The fact that we can flick a switch and 99.998% of the time there is power available, is a minor miracle!
