Jun 22, 2007 6:15 pm
I am currently considering replacing my aging gas hot water service with a Flat Panel Solar Hot Water system. I have heard good things about them but when doing some research on the net came across some concerning developments about solar panels in New Zealand. NZ is different but Australian coast areas are similar.
My concern is that I don’t want to install a unit and have it rust out in 12 – 18 months. The payback period is supposed to be 7-10 years. Hence my concern.
The websites I have been looking at are as follows:
http://www.consumer.org.nz/newsitem.asp ... ng%20alert
I realize a problem in NZ does not mean that there will be one in Australia. The articles do suggest that once the panels are installed that they are out of sight and out of mind. If you don’t carefully examine your gas bills you would not be aware that the system is rusted out and that the gas booster is working ALL THE TIME. If I want a gas booster I will just buy one.
So do solar panels work? AND do they keep working?
Re: Solar Flat Panels - Great? or Gross?2
Jun 22, 2007 7:07 pm
I think you'd have to say a definiate yes to solar hot water being cost effective
The info below I received from the ATA should help with your decision. It was a presentation they did and they talk about rust in here.
What you should do 2
If you're retrofitting an existing home - fit low flow shower heads or flow restrictors, lag accessible hot water pipes.
You can engage a water or energy auditor - some plumbers do this - to check your system and advise how it can be made more water or energy efficient.
When they're due for replacement, select water and energy efficient appliances.
What you should know 1
Solar water heaters come in various styles but all have some sort of panel - referred to as a solar thermal collector - or collector panel or just collector.
In a close coupled thermosiphon system the storage tank is coupled directly to the top end of the collector panel. Heat from the panel rises and heats the water in the tank.
A gas or electric booster is fitted to heat the water to required temperature if the sun's heat was insufficient to do this during the day. This can be in the tank or after the tank
What you should know 2
Alternatively thermosiphon systems can have the tank under the roof, collector piped to tank, same boosting as close coupled system. Might be considered more aesthetically appealing especially but need space in roof cavity that is higher than panels.
What you should know 3
Split system has panels on roof and tank on ground. This requires an electrically powered pump. Blackout will stop pump. Need room for tank close to house. Not always possible to locate it close to bathroom or kitchen where hot water needed,
What you should know 4
Other system types
Evacuated tube collectors - high efficiency, less prone to shading. Better in low light but more expensive than flat plate.
Plastic construction - tank & collector - won't split due to expansion when frozen
Gravity feed - solar systems can be designed for low pressure systems - ask plumber about this.
Combustion heater boosted - also possible but speak with plumber.
Might hear of heat pump - not a solar collector but high efficiency electrically powered heater that operates like air conditioner: extracts heat energy from outside air or from earth using buried pipes and transfers to water. Can be used alone or as booster in solar system.
What you should know 5
Stainless steel and plastic tanks - no corrosion protection required
Glass lined steel - sacrificial anode - aluminium or magnesium rod in tank to prevent corrosion of mild steel - needs replacing occasionally
What you should know 6
Direct or 'open' system - water flows through collector and into tank
Indirect or 'closed' system - heat transfer fluid flows through collector. Heat exchanger in tank transfers heat to water. Needs topping up occasionally. Combats freezing and corrosion
What you should know 7
Electric element in tank - requires J tariff meter and time switch or other control.
Gas heating in tank - needs electricity to ignite flame.
Both systems are thermostatically controlled so don't operate if water already above required temperature. Care needed with electric boost - turned on by timer or ripple signal via 240 V power supply - both controlled by electrical supply company. Might find heater comes on when plenty of sun but supplier wants to dump surplus electricity at a time of low demand.
Gas heating on outlet 'instantaneous'. Temperature controlled - comes on only if required. More powerful heater than tank mounted type - may need high gas flow available to house. Mains gas supply can affect choice of method
What you should know 8
Terminology: Thermo siphon - hot water rises to tank, cold falls and circulates naturally without an electric pump
Tempering valve - adds cold water to hot outlet to prevent scalding
Pressure-temperature relief valve - opens at set pressure to drain water. Protects system against over pressure or boiling. Can cause water losses in summer
What you should check 1
Interesting to know how much electricity or gas you're using to heat water.
Estimating electrical water heating (J tariff) units
Check your quarterly electricity bill for the units (kilowatt hours) consumed.
Divide these by the number of days covered by the bill OR
Read J tariff meter at start and end of typical week then divide by 7 = kilowatt-hours per day
What you should check 2
Estimating gas water heater consumption
Check your Summer quarter gas bill for the total megajoules or cubic metres - although may also include cooking and other gas appliances
Divide these by the number of days covered by the bill OR
Read gas meter at start and end of typical week then divide by 7 = cubic metres per day
What you should check 3
Estimating hot water usage - system supplier will ask for rough estimate - this is more elaborate method than they will need but it's interesting to know:
Bathing habits - how many baths per day?
Measure bath water - (L x W x water depth in cm) divide by 1000 for litres
How long total shower time per day?
Check shower flow using bucket and timer
How many batches of washing per week and what proportion is hot water?
Washing machine capacity - see user manual
What you should check 4
Do you have a section of North facing roof for collector (check Sun at noon)
Is roof angle 40 to 50 degrees (or frame mount)
Unshaded during most of day - is it clear of trees. Check over the day as the sun moves across.
Where is hot water needed? If there's a choice of locations for the collector, pick one that minimises length of hot water pipe runs to taps and the amount of dead water - cold water that needs to be runoff before hot arrives at tap.
What you should check 5
To select the best system for your needs and situation consider:
Tank on roof - aesthetics and roof strength
Tank on ground - available space, how close to taps, power needed for pump
Gas pipe size for booster - measure OD of tube
What is water quality? Is it from mains or bore - analysis by water quality kit or ask water supplier
Is there risk of frost? Can determine whether need a direct system (water flows through collector) or indirect (heat transfer fluid used)
What you should ask 1
From hot water system supplier
Warranty on panel. Warranty on other parts
What happens if there's a power blackout? Circulating pump will stop, gas burner may not ignite
How does booster control work? When does it turn on? How does it ensure all available solar energy is used before using gas or electricity?
How does temperature limiting work and does this cause water losses?
What maintenance is required?
What you should ask 2
From hot water system supplier or others
Government rebates - how much and what conditions?
How does mains gas availability affect choice of boost type?
Ask for explanation of renewable energy certificates or RECs. Government issued certificates to encourage purchasing of renewable energy generating systems. RECs act as a green energy trading system, they have a monetary value and can be sold to businesses who must meet renewable energy targets. Their value might have been already deducted from the price so the retailer does not give you the RECs. Ask this.
What you might ask
Payback period - often asked about concerning renewable energy. Nobody asks the payback period on a new car or a home improvement such as landscaping - or even a university degree. There are many variables - the system cost, how much sun you receive and how much water you use.
Solar hot water systems are environmentally friendly, sun is free, surely it is just common sense. I see plenty of solar collectors in gloomy old England.
And these links should help U too.
Check at the new vacuum tubed solar systems from solarhart too.
Solar hot water units3
Jun 26, 2007 2:47 pm
I would consider evacuated tube solar hot water.
From the research I have done they are up to 40% more effective than flat panels
there are 3 or 4 models available. Check these out:
I'll show you how to keep your new home betwen 15 and 26 degrees celcius all year round - in your buget - GUARANTEED!
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