Google DIY Solar Australia: 2012

Thursday, April 19, 2012

Power Usage vs. Power Generation

You may have taken the time to look at your energy bill, do some calculations of your usage, but how does all that relate a kW rating given for a system?  We have all seen the ads on TV "buy a 1.5kW a 3kW system..." etc. etc.

So now for some information on how much electricity you can generate for a 1.5kW and 3 kW system, and then from these examples examine the reduction in grid energy usage these will achieve.

This will vary upon how close you live to the equator and the (average or mean) number of sunny days per year your region receives.  So this depends upon weather conditions and is therefore dependent on an average prediction.  There is a very good website to help with solar power prediction and in fact will give you comprehensive information.

Experiment with this website if you feel ambitious.

I will use Melbourne as the example location.  Melbourne probably has some of the lousiest weather in Australia, so therefore less sunny days for generation.  Almost anywhere else in this country, the result will be higher.  I live there so I know the syndrome of "four seasons in one day".
Here is the results for a 3kW system:
And the results for a 1.5kW system:
The results give total predicted kWh generated per month. 
If we go back and examine the chart of average daily usage, our consumption for Dec, Jan, Feb was approximately 13kWh per day (peak reading only). Multiplied by 30 days is 390kWh per month, so a 3kW system would provide about the same or more energy than we consume over the Summer months.  Winter is a little more challenging at about 11 kWh per day, 330kWh per month where solar generation would drop to 140kWh for the month of June.  Having said that, average usage in Spring per month is 300kWh so a 3kW solar power system would generate more than we would consume, hence no power bill for that quarter and a return on grid feed in.

So check you bill.  What is your average usage and how much can you cut your bill by installing a solar system? Compare your usage to the 1.5kW and 3kW calculations above.  I would love to hear some feedback, leave a comment below and please share this if you think its worthy.

Tuesday, March 27, 2012

More on Power Usage

In discovering how much energy is used in your house (or premises), most energy bills will show the average daily usage per billing period:

This is the easiest way to determine your energy usage in order to make a decision about what size Solar Power system you may want to choose.

It is still worthwhile either making calculations or purchasing an energy (power) meter as previously described.  Either method will allow you to audit your energy usage.  Why audit your energy usage?  It is an effective way to find out the power usage of each appliance.  You may then identify which appliances use the least and the most power and at what time of the day.
This will then allow you to change your habits of usage, or identify which appliances could be replaced with energy efficient ones.  It changes one's mindset to be energy concious once you spend time examining these things.

Go to my Scribd page to find the spreadsheet that will help with the calculation method.  Often the power consumption is described in different ways, Watts (W), kiloWatts (kW), Amps (A) or kiloWatt hours (kWh).  Any of these can be entered into the table and will be automatically converted by the spreadsheet to kWh.

Some appliances are not used everyday, so depending on the power rating and how often you use it, you may decide to include (or not include) that item.  For example an electric can opener uses 40W and if operated for 5 minutes each week equates to .003 kWh per week.  This turns out to be a much smaller average per day and insignificant to add into your calculation.  Compare this to an electric oven that is 2kW, used for 5 hours per week equates to about 1.4kW per day.

Step by Step guide to Calculating your kWh usage per day:
1. List every electrical item that connects to an electric outlet
2. List every other electrical item not connected to an electric outlet, e.g. electric oven, air-conditioner, electric hot water service.
3. List all of the lights
4. Find out each item's consumption
5. List the times of usage of all items and then the total time used per day.  If not used daily then make an average daily use e.g. 2 hours per week is rounded to 0.3 hours per week.
6. Enter all data in the spreadsheet. You can copy down extra rows if if needed.
7. Get a total from the sum of the last column

I will examine How To's on power meters in a coming post. Also, once you know the daily power consumption, you need to understand how much energy can be generated per day, which will also change throughout the year. This will also require a whole post to itself.

Thursday, March 15, 2012

Size and Power

The most common size Solar Systems commercially sold are around 1.5 or 3 kW.

If you don't know what size you want or need then its best to figure out the power consumption of the house as a basis.  You can then decide to go higher or lower, depending on whether you want to generate and excess to put back into the grid, break even or just save on your electricity bill. The power consumption can be figured out two ways:
  • By Calculation or,
  • By Measurement
Measurement is the easiest method but means you need to connect a metering device to the supply wires, which normally needs to be done by an electrician.  It's reasonable to make an investment in a power meter at this stage because you will make use of it once you have your solar array and system in place.  It may be possible to get an idea of daily consumption by reading your meter daily, at the same time each day for some days - maybe a week.  This will give you the consumption for each day, but will not tell you the times during that 24 hour period when the electricity is being used the most, or the least.  A power meter designed especially will give you lots of information and log the power usage data too.

Using calculation is tedious because you have to figure out the power consumption of every electrical device in the house. This can be done by reading the information from specification plates on appliances or from the appliance's specifications in the user manual. Some things don't have such specification, for example lights, but you can read it from the light bulb.

ASKO washing Machine Specification Plate

I shall publish a spreadsheet to help with calculation, I haven't yet figured a format I am happy with. I will also go deeper into power measurement.

Monday, March 5, 2012

More on Location

There are a few more details to cover on the location of your Solar System before moving on.
  • Non ideal roof layout solutions
  • General form factor of Solar Panels
  • Panel layout on a given roof area
Mounting on an ideal roof slope (North Facing) is normally achieved by fixing the panels parallel (flat) to the roof surface, but with a gap between the panels to allow air to flow underneath.  This assists the panels from getting hot.

For other roof surfaces, we can use an elevating bracket mounting system.

This illustrates an elevated system on a flat roof.  It is possible to also use the elevating system on a roof that sloping east and west.

This is less than ideal as the some of the west side panels will be partially shaded in the early morning and the same will happen on the east side late in the afternoon.  This depends on the pitch angle of the roof. 

A guide to Solar Panel Form Factor.  Solar panels are generally 1.5 to 2 times longer than than they are wide.

It is important to keep this in mind when planning a layout on the roof.  Consider panels that are L= 2 x W.  Placing two panels together with ajoining long sides will form a square.  Placing another two panels with these, ajoining on the short sides of the first two panels forms a L = 2 x W rectangle twice as large as one panel and so on.  Keeping these concepts in mind will enable you to plan how to lay the panels on your given roof area.

How many panels should you use?  This depends on how much electricity you wish to generate.  Currently the most common panels are in the range of 175W to 240W each.

If you have no idea how much electricity you want to generate then a good way to make a decision is to measure the typical consumption of your house.  You will learn how to investigate this next time.

Monday, February 27, 2012

Design and Location

The size of the Solar System you desire and the location of it are dependent upon each other.  Firstly the place to position your system should ideally be both north facing and without shading for more than 90% of the daylight hours.

Lets consider the fundamentals, just a little.  A (photo-voltaic) Solar System produces electricity from light energy.  Whilst I don't want to bore you with details of the theory,  this is the most important fact and so it is important that your Solar System is exposed to the maximum amount of light energy available. This also means that the panels should face the suns rays directly for the best result.

Keeping this in mind, take a look at your home. 
  • Do you have any north facing roof slopes?
  • If so, are they shaded at any point of the day?
Ideally a home with a roof pitched east-west, i.e. sloping to the north (and South) is the best.  If you don't have this, don't sweat it, there are still several options to take.

As to shading, it will really depend on the area shaded and for what length of the day.  You must also consider winter time shading vs. summer as the shadows from an obstruction are longer (bigger) during the winter due to the low angle of the sun.  There are various calculations to determine the difference in shading, this can be difficult for all but the most mathematics savvy people.  So if you are at the summer end of the year or in the middle when you do this it can be difficult to judge.  I will get into the calculations of this a bit later, but for now a bit of visual inspection may suffice. Take a look to the north, north-east and north-west of the place you might use.  Are there any trees or buildings higher than the lowest point of the roof in question? If so, how far away.  A general rule of thumb is in winter, the shadow will be up to about 2 times as long as the object is tall at midday. This depends on where you live: Brisbane the shadow is as long and the object and in Hobart 2.2 times longer than the object is tall.  Take into consideration the height of the roof, so consider objects twice as high as lowest part of the roof in question.

Keep in mind the shadows are longer near sunset and sunrise so this must also be considered.  In all, unless you have large trees like (gum trees) close to the house, this shouldn't be an issue.  Normally, buildings on adjacent properties are not allowed to "overshadow" so this should not be an issue also.  Various parts of your own buildings and the effect they have on your potential location are more likely to be a problem.  As I mentioned, the calculations, if you are in doubt will be covered later.

Your roof is flat, near flat or doesn't have a north facing surface?  Don't worry yet, there are still ways to do it!  For a flat or near flat roof, there are elevating brackets available, these can also be used to some extent on a pitched roof if needed.

The area of available roof to fit panels will detemine the amount of power you can generate.  A typical 180 Watt panel is approximately 1.6m high by 0.8m wide. So you can detemine from this approximately how many panels will fit the area.  For example a 1.6kW system requires 9 panels of this size and so will need 1.6 x 0.8 x 9 sqm = 11 square metres of roof area.

Look out or more details in the next post.  I shall discuss problematic, less than ideal roof areas and other topics.

Wednesday, February 22, 2012

Where to Start with DIY Solar

A few things to consider...this is important to the success of your project.  I am a qualified engineer and these things are part of the project process one way or another, so please consider carefully.
  • Are you willing to do your installation the right way.  I mean make sure that everything you do is as required and not just "near enough is good enough"?  I completely understand at this stage you may know nothing and that kind of commitment is a little overwhelming.  The intention of this blog is to impart the knowledge required to do the job.
  • Are you willing to talk through your plans with an electrician?  This may require some cost for the service but will allow you to check the plans and also have the electrician's buy in to go ahead and sign off on what you complete. You will need to fina a Clean Energy Council Accreditied Electrician if you wish to claim Solar Rebates.
  • Are you willing to persevere?  As with any project you may find a few roadblocks along the way.  This doesn't mean there isn't a resolution, you just need to figure it out and there is help available here.

So I think that's about everything you need to consider before going ahead.  I am willing to answer questions, just submit a comment.

A few disclaimers: The information I impart will inform you on how to get the most out of sourcing and installing your own system.  It is important that you get the right approval (and advice if needed) from a licenced electrician.  I may earn money from any links you click in this blog as I will suggest certain products and services along the way that may help you.

Still interested?  The next things to consider are where will you will locate your system, the size (physical and power output) you desire and the quality of the components you wish to invest in.  Stay tuned, I will address these things...

Monday, February 20, 2012

DIY Solar Australia

Hi there

This blog has arisen in the light of the changes in the solar uptake in Australia since the Government has cut the Funding for home solar installations in 2011.  Those of you who genuinely want to contribute to reduction of greenhouse gases and save money but may find that now the cost is stopping you from going ahead, please read on...

Now that the cost of a system is increasing, its desirable to look for ways to cut the costs.  There are several possible ways to do this and probably the best way is for you to take control of your of you own installation, rather that relying on another company to entirely supply, install and connect your system.  I personally don't want to leave my solar system in the hands of a company that may not exist in 10 years time, let alone may not be around next year.  We must keep in mind that a solar system should last 30 years or more and if you plan to stick in the same home for that long (as I do) then this is an important point to remember.

Do It Yourself Solar in Australia.
Despite the rumblings of various authorities in the arena, there is no reason why its not possible for the average adept person to install their own Solar Array.  I say this under the caveat that the job must be done in accordance with the required standards and that only a licenced electrician can connect to the mains power of your house and make the connection for providing energy back into the grid.

In This Blog I will detail how this can be achieved.  I am committed to showing the people of Australia alternative ways to generate alternative energy.