West Facing Solar Hot Water System?

If you are committed to sustainability then space on the North facing roof is at premium.

One option may be to look at putting the solar hot water system on a West facing roof.

This will mean you can maximise the space for north facing Photo Voltaic (PV) solar panels.

Although the solar hot water system will not be quite as efficient there are a couple of reasons why it is a worthwhile option.

    • If you check the solar alignment post you will see that its possible to get around 80% of the maximum efficiency compared with a North Facing system.
    • For most families the time when you will be using most hot water is the evening and early morning. The West facing system will have less time to lose heat before use than the North facing system.

I’m not saying West facing is best but it can be a good compromise.

 

For more Green Ideas see Sustainability

 

Solar Hot Water

With the current emphasis on building efficiency solar hot water systems are pretty much a standard option if not automatically included.

These systems incorporate either gas or electricity boosting for cloudy days.

Here are a few thoughts on the options for solar hot water:

Split System or Tank On Roof

  • Systems with Tanks on the roof are the most efficient . They don’t need a circulation pump to circulate the hot water to the storage tank and don’t have long pipe runs that lose part of the heat you have collected. If this is the way you decide to go make sure your roof has been designed to take the load.
  • Split systems are easier to service when they go wrong as everything other than the panels is at ground level. Many people also prefer the look as they don’t like the large tank on the roof for aesthetic reasons.

Flat plate or Evacuated Tube Panel

  • Evacuated tube systems are more effective. Also from comments on forums I hear 2mm evacuated tubes are stronger than flat plate collectors in the case of large hail, and are less likely to be hit square-on, due to their shape. Just make sure you aren’t getting cheap quality thinner walled tubes.
  • Modern good quality evacuated tube and flat plate systems should be essentially maintenance-free. Just make sure of the quality, it can cost $300-$400 in labour to replace a defective panel even if the actual panel is replaced under warranty.

Insulation

Some of the early Solar water systems only insulated the hot water coming from the system. This is poor practice as once the system starts running the water from the storage tank back to the panels warms up. If this cools in the pipes to the panels you will be loosing efficiency. Make sure you have all pipes insulated.

Boosting Systems

  • I think Gas Boosting is probably the best way to go even if you have the higher priced bottle gas rather than mains gas. This is because gas systems only boost the water when you want it rather than electricity where you are heating the whole tank up even if you are only using 10% of the contents.
  • If you `go for electricity its best go for an off peak boosting, but only switch it on if the forecast is for cloudy weather.

 

See why a West Roof Mounting may be worth thinking about

For more  information on choosing systems for your new house see  ‘Selection / Pre-Start Guide’

 

Block Orientation

Sponsored by Coral Homes

When looking at block orientation a key issue is using the sun to warm the house in winter and keeping the sun out of the rooms in the summer.

Typical blocks in Australia are rectangular. About twice as long as the block width, as are most home designs. This limits the way you can place the house. In my experience the order of preference of blocks is.

1. Facing East
2. Facing West
3. Facing South
4. Facing North

If you have got a block at an angle it will require a bit more thought unless you can orientate the house in one of the above preferred directions. Larger blocks and square blocks make adjustments to the house orientation easier.

My reasons for the preferences are as follows:

Facing East

This orientation allows one of the long sides to face north making the best use of the sun in a passive solar house. Usually the master bedroom is at the front so even in the summer the low sun morning sun only warms the bedroom from the chill of the night. Windows can be minimised on the west side to stop the house overheating in the afternoon and evening. This orientation also gives you plenty of roof area for the most effective location of solar hot water and solar electricity panels.

Facing West

Again like the east facing block you can have one of the long sides to face north making the best use of the sun in a passive solar house. With a master bedroom at the front you will need to take steps to keep the afternoon sun out of the room to stop overheating. Like the East facing orientation this is useful for solar panels on the roof.

Facing South

With a house facing south the best layout is to have as many rooms as possible having large windows facing north which can be difficult on a narrow block. To make the best of this orientation you may need to have plans drawn up as most standard plans don’t suit this orientation. It’s also best to minimise west facing windows.

Facing North

A north facing house is probably the least desirable on a suburban block as it makes it hard to get the sun into the house. I certainly wouldn’t want big north facing windows allowing passers by to look in.

 

Lots more information in the anewhouse Guide to Buying a Block for only $4

See similar posts see Choosing a Block and Passive Solar

 

Solar Electricity – Is It Worthwhile? (2011)

Since this post was written in 2011 there has been many changes; in subsidies, the cost of systems, and  Power Supplier charges. For the  an updated post see:  Solar Electricity – Is It Worthwhile? (2014)

There is a lot of marketing information around about Grid Connected Solar Panels but not many facts. Here’s how I evaluate a basic system for a house in a Melbourne Suburb.

  • We uses around 16kw hours (kwhr) of electricity per day which is fairly typical;
  • For each 1kw of solar panels we can expect to generate around 1300kw hours per year that’s an average around 3.5 kw hours per day;
  • For the basic 1.5kw system we should generate on average about 5.2kwhrs;
  • Our current tariffs for power is $0.2025 /kwhr regardless of time of day;
  • I Have done the evaluation assuming that any surplus power is sold back at the peak rate. Some states have attractive buy back rates that will improve your financial situation.
  • As part of going solar our tariffs will change to:
    • $0.2625/kwhr peak times (7.00am -11.00pm Monday to Friday, 80 hours per week)
    • $0.1075/kwhr off peak (all times other than peak, 88 hours per week)

How Much Will Be Saved?

As we are out of the house for at least half the peak period the cheaper off peak power should more than offset the more expensive peak power so our average power cost should remain similar to our current tariff.

Weekdays (as we both work and the house is empty during the day) we should be able to put at least 2.5 kwhrs into the grid and use a maximum of 2.7kwhrs running fridges etc)

Income 2.5kwhr @ $0.0.265 = $0.66

Saving 2.7kwhr @ $0.2625 = $0.70

Benefit = ($0.66 + $0.70) x 260 days = $353

Weekends we probably will only put 1kwhr into the grid as we may well be at home using power for TVs, heating and cooling, etc.

Income 1kwhr @ $0.265 = $0.265

Saving 4.2kwhr @ $0.1075= $0.45

Benefit = ($0.265 + $0.45) x 104 days = $74

Total annual benefit is $427

(I believe my calculations have been fairly conservative and the actual benefits could be higher) PLUS For every $0.01 of premium rate buy back you will get another $6.24 per annum.

Is it worth it?

Well there are some 1.5kw systems being advertised now with various rebates which cost less than $3000.

If you had $3000 on term deposit it would now (Jan 2010) be returning 6% that’s $180 a year, which would then be taxed. Alternatively if you put the cost on your mortgage that will mean that you are borrowing $3000 at a rate of around 8%. That’s costing around $240.

From these figures it looks like for the basic system we could be around $187 better off. Even more if you spend less than $3000 or can get a premium buy back rate.

If you are looking to get a system you need to know that there may additional charges for things like:

  • Installation on a tiled roof;
  • Frames on a flat roof to provide the best angle for the panels;
  • Split array over two different sections of roof;
  • Lifting and access if you have a 2 storey houses;
  • and travel charges if you are outside the metropolitan area.

For similar posts see Solar Electricity in the Sustainability Tab