Solar Option is eager that purchase and installation of any solar product should be treated as an investment, be as cost effective as possible, and therefore give a return on investment (ROI). To have reached this page indicates you are eager to find information that may clarify some of the hype or mis-conceptions about solar.

Only 'Go Solar' if you are prepared to have it installed in the correct manner for it to function efficiently. There are already far to many 'pretend' solar installations around.

Solar products do not function the same for everyone! Installation determines the maximum efficiency it can attain (and at what time of year this occurs), dictated by solar access, orientation and the building (or imposed) constraints/limitations, at the location.

©2012 Solar Option

The articles on this page are intended to present facts about functionality. Please send feedback if they tend to confuse, or you require further information.

Topics:

Why should anyone consider solar energy?
Solar Collector Tilt Angles.
Passive Sun Control.
Greenhouse Gas Calculator.
Passive Solar House/Block.
Photo-Voltiac Basics.

Why should anyone consider solar energy?

Solar energy (including resultant energy from wind, hydro and wave) is the only form of energy that is free for personal capture/use. Once the initial outlay for equipment is recouped, future energy is virtually free (apart from possibly a small cost for ongoing maintanance of the system).

This means at some point not only will the system have paid for itself but give an ongoing return on the investment. This is not a gamble like shares or other forms of investment, but a certainty (though time period is variable) dictated by your commitment.

All other energy saving purchases you make (vehicle, fridge, washing machine or TV) may reduce your energy use (and only that), they will never return a profit.

There are two components to energy saving, financial and environmental. The financial saving benefits you, the environmental saving benefits all on this planet.

The most common solar energy systems are water heating, which have been available for many decades, and power generation using photo-voltiac panels, which have only become widespread in more recent times.

The use of solar energy for water heating gives the most efficient conversion of solar energy for domestic use, and as hot water is a large component of home use it makes sense to consider installing this as a priority. Solar can provide close to all your year around hot water requirements if done correctly.

Power generation is a good way to offset electricity use and cost (which will continue to increase over time), but in most cases will only provide a small proportion of your total energy use.

You will still need to include energy reducing practices to maximise benefits, which will also effect the period of time to achieve system payback. Generous goverment rebates are currently available and make purchase affordable, while they last. They will never be more generous than now!

Some energy suppliers offer 'feed in' schemes where they purchase energy developed by your (PV only) system where the units exported tariff is higher than that of units purchased from them. This can both reduce your energy costs and encourage further energy reduction (to maximise returns).

There are different methods by which you can get a return on PV investment and obtain an ongoing return. You can get a ROI by just reducing the amount of electric units purchased (by the units generated) or participate in a 'feed in' scheme. This will be either 'total produced' or 'amount exported'.

Most people like the idea of the 'total produced' scheme as you get paid for all units your system produces. This does give the maximum ROI, but does not encourage energy reduction as you get reimbursed regardless. On the 'amount exported' scheme, you only get paid for the amount you export, in excess of usage at the time. This does encourage energy reduction, in order to export a greater proportion of what your system produces.

The 'amount exported' scheme is the better option for the environment. Your energy supplier will dictate which option (if any) is available.

Both Solar Water Heating and PV systems qualify for Renewable Energy Certificates (RECs), a refund which is a monetary value for the energy efficiency of the system calculated over a fixed time period. The value of these certificates is variable and may become more transparent (and possibly higher) when/if a fixed price for carbon is established.

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Solar Collector Tilt Angles.

This information is assuming your collectors have good solar access (see SACI) and face due North.

Though both photo-voltiac (PV) panels and solar water heater (SWH) or air-heater collectors can look similar and require direct sunlight, for maximum efficiency each has its own ideal tilt angle, as they are designed for different purposes.

As photo-voltiac panels are expected to produce the maximum (total) kWhs throughout the year, they are best suited to a relatively flat tilt of about 20-25 degrees (most roof pitches). This is because the longest daylight hours are during summer, which is also when the sun is at its highest and solar energy (insolation) at its greatest. If you have air-conditioning it is also the best period to offset electricity usage. Whereas solar water heaters are required to function at their highest efficiency during winter, and therefore require a steep angle.

Applicable rebates may 'sweeten' the move to solar, but do not offset efficiency lost through bad installation, or make it any more of an investment. Eventually any lack of efficiency will result in a cost to the end user (purchaser). Most 1kW PV systems will only reduce household electricity use and gain little (if any) from the present utility buy-back scheme. However, it is beneficial to the utility, as it delays their need to upgrade infrastucture for increased capacity.

The rest of this article is aimed at solar water heating collectors (see article #5 below, for photo-voltaic panels). Water heating is currently the most efficient use/conversion of solar energy, so don't lose that benefit through bad installation.

A correctly installed solar water heating system may cost the same overall (product+install+running) after twenty years, that a poorly installed system may after only ten years (which may also require replacement around that time). In the second case would you go solar again for the replacement? I doubt it.

Solar water heaters are solely designed to deliver hot water. However a poorly installed electrically boosted solar water heater could more accurately be described as a 'solar augmented electric water heater', as the booster does most of the heating in winter, when hot water requirement is greatest, and the collectors should be functioning at their best.

There is a large difference between total annual input, and input corresponding to usage. The difference (apart from orientation) is mainly related to the collector tilt angle. You can find an additional pdf (0.4mb) describing tilt angles for solar water heating collectors here, though most details are covered in this article.

Though it is true that having water heating collectors on a shallow tilt you get the highest total (annual) input, it comes with a penalty. As you are probably not using the hot water as much during summer, it puts extra stress on the system, shortening its expected useful life, unless you climb on the roof and cover part of the collectors during this time. Then during winter the sun is to low for useful input for most of the day, requiring excessive booster use to compensate.

The time of year that most hot water is used is during winter, therefore the collectors should be set on a steep tilt (about 55-60 degrees) for maximum input at this time of year. This maximises surface area exposure and reduces reflection, as the sun is always below the mid-day altitude. This will minimise the need for the booster to heat water on short daylight hour (and cloudy) days near the winter solstice. This results in a lower overall/annual input, but delivering a more appropriate, time of use input.

On a steep tilt efficiency drops during summer when considerably less hot water is used (whilst still providing more than enough), helping prolong system lifespan, due to there being less surface area directly exposed, and increased reflection. With the sun higher in the sky, more daylight hours when the sun is more intense, loss of input is not a problem as hot water use is low during this time.

Overall a SWH collector tilt of 55-60° (in Perth) gives a more even input throughout the year, with significantly more input during colder months and lower input during hot months, than collectors at a low tilt angle. The system can be more accurately sized for its task in winter, in the knowledge that it will not suffer substantially during summer.

Solar energy is weakest close to sunrise/sunset, reaching maximum around mid-day. Collectors may be far colder than the tank temperature in the morning, so have to use the solar energy just to reach the tank temp, before any heat is available for input. In winter there may be far less than 0.9kW /m2 (maximum) energy available, whereas the electric booster has around 2.4kW available immediately.

Boosters will always overide solar input due to their immediate availability of energy, so should only be used manually, or work via a timer. Otherwise the booster heats the water quickly, and for the rest of the daylight hours the collectors have nothing to do. Any heat the collectors do contribute beyond the booster cut-out temp (most evident in summer), may just contribute to shortening the system lifespan.

The Solar Saver was a retrofit designed (by Jay MacFarlane) to automatically give preference to the collectors if it detects there is enough solar energy in the morning to heat the water (slowly) throughout the day, by turning the booster OFF. Whenever there is not enough solar energy available (cloudy days) the booster switches ON as normal.

It has become apparent that the lesser known Evacuated Tubular Collectors (ETCs) are far more efficient than standard flat plate collectors, for heating water. They start to contribute heating early in the day, have close to maximum input for the majority of the day which only drops late in the day. Whereas flat plate panels start more gradually, reaching maximum input around midday, and tapering off afterward (a regular bell curve). Prices may be slightly higher for ETCs but the efficiency benefit makes them cheaper overall, with an earlier ROI.

Raising the collector angle for maximum winter input is applicable to both flate plate and ETCs. However flate plates offer a solid surface (sail) to the wind, whereas ETCs allow the wind to pass through. It may also increase surface losses to flate plates (temperature dependant), which causes little effect to ETCs (due to their vacuum insulation).

A recently conducted energy audit has shown that; if you currently have a servicable gas water storage heater, you are far better off (financially) sticking with it, than changing to an incorrectly installed electric boosted solar water heater. Don't be swayed by a salesperson trying to convince you otherwise. Only when the gas unit has to be replaced, does changing to a correctly installed solar water heating system become an investment.

If you have a solar water heater on a low tilt angle that is under-performing during winter, don't be tempted to increase collector area unless you are prepared to place a partial cover on the system during hot months, or you will just reduce its lifespan even quicker. Solar Option is developing a system to expand the collector area for winter input only.

Some people that do not wish to install on a north-facing roof (due to aesthetics), or do not have a suitable north-facing roof, attempt to rectify this by installing on a frame to restore correct orientation. Unfortunately almost all of these frames still use a low tilt angle. Not only does it cost extra to install, but it still doesn't provide maximum efficiency when needed most, or prolong system lifespan. If you do consider a frame, make the extra cost worthwhile by installing at the correct high tilt angle to ensure system efficiency and longevity.

The ultimate setup requires a tracking system to follow the sun for maximum efficiency (about 30% better than a fixed system of equal size). Not only can it get the highest efficiency when required but can also 'hide' when not required.

If you are unable or unwilling to install SWH collectors in the correct manner, and your only alternative for heating water is electricity, the next best option is a heat pump system. This works in an opposite manner (but same principle) to your refrigerator. It takes available heat from the air and transfers it to the hot water tank.

Though it still uses electricity for its operation it is approximately 3.5 times more efficient than the heating element normally used in an electric storage system. There may not seem to be much heat available in the air on a cold winters day or night, but the heat is not relative to the 0c to 100c range that we normally relate to, but relative to absolute zero (-273c).

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Passive Sun Control.

Though Solar Option manufactures the SUNGOLA passive sun control, handy persons may like to try their hand at making their own version.

You will find a brief pdf (0.4mb) description of how such a structure is designed here. Actual angles and overlaps are not shown as they are specific to the latitude of the location.

The SUNGOLA can be supplied as a completely knocked down (CKD) kit for those wishing to undertake their own construction. This is the normal supply method used outside the Perth metro area (Three Springs to Esperance). The kits include all components, assembly drawings and instructions.

Corrugated metal sheeting gives 100% shade all year around, hit/miss battens and shade cloth create more shade in winter than summer.

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This document relates primarily to Perth, Western Australia.

A 'solar pergola' (generic term) is a shade device, it does not generate electricity but adjusts shade throughout the year, in relation to the suns' path across the sky.

Greenhouse Gas Calculator.

Steve has collaborated with Ben Rose to produce a Green House Gas emissions calculator (Windows only) for use by Australian households.

The project started when they both belonged to the Warren Districts Renewable Energy Group (WDREG). At which time the group was undertaking one of the 20 Cool Communities projects around Australia (3 in W.A.), aimed at encouraging households to reduce their energy consumption. The Cool Communities projects were funded by the Australian Greenhouse Office and supervised by the Conservation Council.

Ben had already been developing a spreadsheet to calculate greenhouse gas emissions attributable to Australian households. Steve liked the information that it could show but (like others) was not sure that a spreadsheet was very user friendly, so as an amateur programmer attempted to develop a stand alone version.

After demonstrating the (very buggy) initial version at a WDREG meeting, the two decided to develop it further. Once most of the bugs were removed, the original version was made available on the WDREG website. Over time it has expanded to enable more data to be input, to give a more accurate result while still sticking with an easy to use interface. Initially designed to fill a 800 x 600 screen (to minimise scrolling), this has since been increased to 1024 x 768. Unfortunately programming skills still remain minimal.

The screen layout is arranged with the highest emitting section at the top, decreasing down the page. Most of the items are multiple choice, with input of quantities required. This can be done as a quick guesstimate for one section, or a sit and think total household estimate. Some sections contain sub-sections for more indepth input.

Ben has stuck to his principal of giving the whole picture, rather than massaging results to promote any particular group agenda. The program also functions as an energy calculator.

Though quite logical to use as is, there is plenty of on screen information, supported by an extensive help file, giving more than just program help/instructions. By downloading and running the program, results are shown immediately, whereas online calculators have a short pause between actions, and are mostly aimed at a particular interest group rather than a more realistic overall picture.

More in depth information can be found at Ben's website.

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download GHGcalc5.zip (0.5MB)

After un-zipping, move the complete folder to a suitable location.
Go to Ben's website for more details on environmental sustainability.

(Original version of GHGcalc)

Passive solar houses/blocks.

Orientation is crucial for a passive solar house to function correctly, but siting on a block is dictated by the block/house size, orientation and local council set-backs.

Though councils are supposed to require that new developments are environmentally sound, just look at the layout of developments approved over the past few years, to see how few attempt to encourage this. When looking through the street directory, it is easy to see how few councils are attempting to make passive solar housing more accessible.

When choosing a passive design, it can only function correctly with correct orientation. For ease of layout, the vast majority of blocks are rectangular and run parallel/perpendicular to the street. All councils have their own fixed set-backs parallel to block boundaries and as a result most houses also coincide with street direction.

Gone are the days of the 'quarter acre block' (about 1000sqm), where a large house could fit easily with plenty of distance from set-backs on almost any orientation. Most new houses struggle to fit within set-backs, forcing house orientation to exactly match that of the block. If your design has to be re-aligned to comply with set-backs, it may no longer function at the designed rating.

A developers primary focus is to maximise their investment by getting as many blocks as possible out of a parcel of land, not provide ideal blocks. Councils just rubber stamp developments, to maximise rates from the overall development containing the maximum number of rateable blocks.

It's not that parcels of land contained within poorly aligned streets can't be divided into blocks with good orientation, it's because there is no incentive to do so, people just buy what's on offer as that is all that is available. With greater information about the blocks available to the buyer (not just size), decisions on purchase would be made easier. It would indicate to developers what the public are really looking for, as less desirable blocks would be hardest to sell.

Should you intend installing PV or a SWH (initially or in the future), correct roof orientation and area has to be available, or it may not be able to function efficiently (or to its maximum capacity). This will be (most likely) primarily determined by the block.

How to rectify this.

I have submitted a proposal (to ABCB) that there should be a star rating for blocks, to enable purchasers the option to match the block with/to their house design. This would give confirmation that both block and house are compatible and able to fully utilise the house rating. A star rating would also indicate that the developer is environmentally responsible, by providing such information.

The block star rating would encompass; block size, aspect ratio, block orientation, topographical situation, shading (by permanent structures) and local council set-backs (which may not otherwise be obvious prior to purchase).

There are energy star ratings for washing machines and fridges, which can hardly be classified as major purchases, though they do have an ongoing energy requirement/cost. The house and land (package) is not only THE major purchase but also THE major ongoing energy consumer, required to provide lifestyle comfort (heating/cooling and lighting), and therefore far more important for assurance of efficiency. The house rating alone is only part of the package and can not exist/function correctly without a compatible block.

Though homes are now designed to comply with a minimum 5 star rating, this may be greatly reduced through incorrect orientation, due to poor block choice/availability. Therefore being able to match the house with a compatible block makes for good sense and an overall (lifetime) saving.

As more purchasers request 5 (or more) star blocks it should encourage developers to provide more ideal blocks (as they will probably sell for a premium). Getting less for low star rated blocks, should promote more environmentally friendly layouts, as a block with a low star rating would indicate to purchasers that problems are evident, prior to purchase. Making it difficult to 'off-load' bad blocks for good money.

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Photo-voltaic panels - the basics.

Solar water heating panels and photo-voltaic panels (despite using the sun) are entirely different in their operation, though from a distance they may look similar, as do solar air heating panels. Water heating panels (see article #1 above) transfer heat energy from sunlight to the water in the panels, whereas photo-voltaic (PV) panels convert the light energy (photons) into electricity. The following article looks at photo-voltaic panels.

In the article on solar water heating I mentioned installing at a high tilt angle, the opposite applies to PV. Though it is still beneficial for input during winter you get the highest input during summer, which is the ideal time to offset your energy use/cost or maximise return if you are on a buy back scheme.

To lessen confusion by consumers, PVs are 'packaged', as there are lots of variables to be considered. As they relate to electricity, the panels are rated in Watts (W). The rating is the peak power output of the panel under a fixed set of conditions, and is generally a world accepted standard. This does not mean they will function exactly the same anywhere in the world, as the weather conditions they are exposed to will be different.

Sticking with electricity, everyone can relate to the old light globes that have existed for most/all of our lives. You generally choose a low wattage (25w) globe for a small room, up to a high wattage (100w) globe for a large room, or multiple globes for a very large room. The consumer does not need to know how that figure is arrived at, only that it is a figure that can be related to when purchasing a globe.

Likewise PV panels are sold on their rated wattage output, though most people will purchase multiple panels (an array) to give an overall output, usually in kilowatts (kW). You may notice that 1kW arrays have between five and seven panels, depending on the output of the individual panels. Each manufacture has their own selection of prefered sizes, for their production process.

Just as cars come in different types (sedan/4WD/formula-one) PVs are not all the same. There are basically three types: Mono-crystalline, Poly-crystalline and Amorphous (thin film). Mono-crystalline came first, and as the name suggests each cell is constructed from a single crystal. Poly-crystalline came next and is composed of many crystals. Finally came Amorphous, which is composed of very small particles deposited in a thin film.

Each type has a different 'efficiency' (the amount of sunlight it can convert into electricity). Mono-crystalline are highest at around 20%, Poly-crystalline around 17% and Amorphous around 10%. As panels are sold by their output rating, the size of the panel is related to its efficiency. The higher the efficiency, the smaller the panel. Therefore a 1kW array of Mono-crystalline (20%) panels will require around half the area of Amorphous (10%) panels.

If available roof space is limited, or you may be considering adding more panels in the future, Mono-crystalline should be your first choice as they have the highest efficiency. Not all suppliers sell all types. Once you have committed to a panel type you are stuck with it, as different types should not be mixed.

You can usually pick the panel type by their appearance. Mono-crystalline are mostly black cells (round or square), Poly-crystalline are usually blue-ish square cells, and Amorphous are more of an overall (brownish) panel colour.

Generally panel efficiency is reflected in the price, but the difference is not great considering the overall cost of a system, be it grid connected or stand-alone (battery storage). As with any product, there are quality differences between manufacturers and countries of origin.

Panel efficiency is reduced by dust on the panels and panel temperatures above 35°C. Shallow tilt angles and lack of air flow around the panels increases the panel temperature in summer as well as the likelyhood of dust build-up. An occassional clean with lightly soapy water helps to remove the dust (especially during long dry periods) and maintain efficiency.

Incorporating PV panels into the roof is not recommended as roof cavity air can be way above the ambient outdoor temperature in summer, keeping the panel temperature artificially high and reducing efficiency even further. They should be raised clear of the roof to facilitate cooling, though this will possibly still be above the ambient outdoor temperature. This does reduce the area of roof (beneath it) being heated by direct sunshine.

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