Newsletter Archive

E-News Issue #132

Feb 9, 2010

A Few Renewable Energy Stats

According to a 2009 Clean Energy Council Report:

  • in 2008 the Solar PV Industry employed 3940, and solar hot water (SHW) 1750 people.
  • Australia has a 16% RE capacity but was only producing 5.8% last year as a result of low rainfalls in the hydro sector
  • Solar PV installed capacity is 145 MW generating 262,800 MWh/year
  • About 7.6% of Aussie homes use solar – PV or SHW
  • There are 1526 accredited solar installers

According to the Australian Bureau of Statistics, there were 153,600 homes with Solar PV, the SHCP rebate resulted in 50,000 more homes to Oct 2009 with a further 70,000 to be installed. By the end of 2012 there should be 275,000 homes with solar PV, and 1,000,000 with a solar hot water system.

By the way, don't get too excited about the Federal Liberal Party promised solar rebate, if it gets elected – it is $1,000 for either PV or SHW!!

Refrigeration for Solar Systems

Refrigeration has been a recurring theme for articles in the e-newsletter over the years. This is because nationally, it represents some 11% of the nations domestic energy usage and on stand alone systems (or off-grid systems), it is often 2 – 3 times this figure. The panels and batteries to run a large fridge can cost up to several thousand dollars.

Fridges - The Gas Option

LP gas fridges are an option – a 220 litre fridge freezer will typically use a large bottle of gas every three months so the yearly running cost is close to $500/year. There is some maintenance to keep the gas jet clean, the fridge fumes should be vented outdoors and a gas fridge can struggle a bit in tropical heat. The gas bottle can run empty at inconvenient times of the day or night. Some of these fridges are often known as 2-way or 3-way in that they can also run off 12V or mains power electricity. These use the electricity to first make heat similar to the gas flame. Depending on size, they typically draw 10 - 25A @ 12V and will run non stop for 24 hours per day. This type of fridge is okay to run on gas but is too power hungry to run it off solar.

Fridges - 12/24 Volt Fridges

There is a fairly large range of small chest fridges made mostly for the camping market. The better quality ones use a Danfoss compressor. There are also a few very efficient larger chest fridges made for specialist applications. These can often cost $2,000 – 3,000. Their appeal as a ‘family fridge’ is limited, however some are very energy efficient. Most are either a fridge or a freezer. If it has both, most have a very small freezer.

A further innovation is the use of eutectic fluid in some of these fridges. In the old days this used to be a brine solution. The idea with the eutectic fluid is similar to the esky freeze packs you put in your deep freeze for camping trips.

Eutectic refrigeration is often used in fishing vessels. The basic principle is that when the engine of your boat or vehicle is running (and therefore generating power), you run your fridge so that the eutectic fluid goes below 0°C. This then keeps your fridge cold for a further 24-48 hours (while your engine is off). The advantage of a eutectic fridge in a solar set-up is that you can time the fridge to come on in day light hours only (when your solar panels are generating power). This lowers the system voltage a bit and helps to get a bit more amperage from your panels. More importantly, it helps reduce the battery inefficiency which results from storing power in your batteries during the day to run the fridge at night! And the last bonus is that 1-2 days holding capacity of your fridge is a bit like having some more battery storage. We have monitored a 73 litre eutectic fridge (chest type) for a one year period in our area. If you are not familiar with our location, Nimbin is fairly close to Brisbane. Basically it is a sub tropical climate with typical summer day temperatures around 32°C and winter day temperatures about 20°C. The average daily current consumption @ 12V in Winter is 8 - 11 Amp hours, in Spring & Autumn = 12 - 16 Amp hours and in Summer = 17 - 20 Amp hours.

There are also a number of upright fridges made. These generally use a standard 230V type of fridge cabinet fitted with a Danfoss compressor. These are expensive – approx $2,000 for a 220 litre model.

Until a couple of years ago, it was generally agreed that if one wanted an upright fridge on a solar system, one needed to buy a 12/24V one which was expensive with limited choice of models and features available.

Fortunately for both the environment and those living on off-grid systems, 230V fridges have been getting more efficient over the years. Virtually any fridge you buy today uses some 50% of the power that a typical fridge used a decade ago.

Fridges - Star Label Efficiency Ratings

All 230V fridges sold in Oz must be tested for efficiency and labelled according to AS/NZS 4474.2. They show a number of Stars to give the lay person a good idea of what models are best - the more Stars, the higher the efficiency.

For those with more advanced electrical knowledge, the label also gives the power used per year (kWh/year). This figure is very useful to us when designing a stand alone solar system. We usually divide this yearly figure by 365 to get a daily figure.
The test standard for a fridge measures the power used to maintain the test temperature for a 24 hour period with an ambient temperature of 32ºC for a full 24 hours. This includes the power used for auto defrosting. The inside temperature is first standardised at 3ºC and -15ºC for the freezer, no food is in the fridge and the door/s are kept closed throughout the test. While this is just a test standard or bench mark that appears to be somewhat unrealistic, I have been told that it approximately simulates the average usage pattern in an average house in an average location in Australia.

Some years ago we tested a number of fridges in ‘real life situations’ and we generally found that they used less in this area than the Star label indicated.

In the past week, we have tested 3 fridges to compare the Star label usage verus a real life usage pattern. The three fridges tested were:

MakeSizePower SystemStar LabelRPC Test
Waeco 220 litre 12/24V – new 1100 Wh/day 980 Wh/d
Westinghouse 190 litre 230V – 10 years old 1068 Wh/day 960 Wh/d
Electrolux 420litre 230V – new 956 Wh/day 890 Wh/d

The RPC test was conducted for 3 days at room temperatures between 24 – 29º C. The Waeco was first brought down to test temperature with four 6 packs of drinks inside. There after, power was measured by removing one six pack and replacing it with a room temperature one daily. The door was opened 6 – 8 times a day. The Westinghouse and Electrolux were tested in my home ie one person using them. Interestingly, the RPC test results were 89 – 92% of the Star label for all 3 fridges tested.

Find Star Label ratings for all 230 volt fridges sold in Australia. You can narrow your search by fridge type, capacity & brand. You can then alter the sorting by size, efficiency etc. Also there is a Tab for "Comprehensive Detail'.

Fridges - The Most Efficient 230V Refrigeration

Electrolux is the Aussie winner in this category with their Eco range of fridges and freezers. They are the only range of refrigeration in Australia with both a 5 Star (current rating) and 3.5 Star (new rating). The Eco range is made in Australia. Their upright fridges are from 420 litres up to 700 litres and they also have a 360 litre upright freezer. They all use a new non-synthetic refrigerant R600A.

There are quite a few models, including;

TypePower
420 litre fridge/freezer (top freezer) 349 kWh/year
430 litre fridge/freezer (bottom) 406 kWh/year
520 litre fridge/freezer (top) 402 kWh/year
700 litre fridge/freezer (side by side) 525 kWh/year
430 litre fridge only 250 kWh/year
360 litre upright freezer only 403 kWh/year

Alternative freezers include Fisher and Paykel, Westinghouse and Lemair who make 200 – 216 litre chest freezers using between 334 – 349 kWh/year.

In the fridge range, leaving out a couple of imported fridges costing several thousand dollars, the nearest 'energy competitors' would be;

BrandSizePower
Fisher and Paykel 380 litres 433 kWh/year
Westinghouse 365 litres 495 kWh/year
Samsung 238 litres 338 kWh/year

Fridges - AC versus DC

The advantage of a DC fridge is that they are generally quite efficient and you don’t need an inverter which can result in some 15% efficiency losses – probably less if lights, TV etc are on at the same time.
The inverter will probably need to be left in ‘Run’ or ‘On’ mode, rather than on ‘Standby’ to keep the electronics running in the fridge. This could typically add a further 180Wh/day to your daily load. However you may want to have your own inverter on anyhow to keep LCD clocks etc going on appliances.

Your inverter may need to be larger than you would otherwise need. The 420 litre Electrolux uses 161 Watts when on and up to 1790 surge on start up.

These 3 power consumptions were measured in the USA:

Run PowerStart/Peak PowerType
150W Run 1,900W Peak fridge over, non-frost-free
200W Run 2,400W+ Peak Side by Side, ice maker, FF
200W Run 2,300W Peak Side by Side, ice maker, FF

If you are happy with a chest fridge, then a 12/24 Volt DC fridge is probably your best bet.

However, once your desire reaches to a 220 litre or larger upright fridge, you really need to consider the 420 litre Electrolux. Its power consumption compared with the 12/24V Waeco fridge is about the same even considering inverter losses, it is stainless steel and almost twice the volume for $400 cheaper!

You can see from the above example that the Electrolux may be the way to go if you want an efficient 230V upright fridge. The only disadvantage with the Electrolux range is cost – about $1,600 for the smallest 420 litre model. They are an upmarket range, with a stainless steel finish, glass shelving, ice-cube maker etc.

You might get a more economical white fridge for perhaps $600 cheaper that uses an extra 100 kWh/year. If you are on the grid, the yearly cost is another $22. If you have a stand alone, or off-grid solar system, it would mean an extra $1,000 – $2,000 worth of solar panels and batteries, so in other words it is cheaper to spend an extra $600 for the Electrolux fridge.

We are often asked “what is required to run a fridge only on solar panels”. To run a 349 kW/hr per year fridge, ie the large 420 litre Electrolux, would require 450 Watts of PV solar panels, and 500Ah @24V battery storage with a 700 Watt inverter assuming that nothing else is running off the inverter.

Oh, and by the way, I don’t have any shares in Electrolux! nor does Rainbow Power Company sell any 230V appliances.

Fridges - Home Monitoring

If you would like to measure your 230V fridge or other appliance power consumption, purchase of one of our energy monitors.

Conclusion

  1. The Star label gives a good indication of expected power consumption. Actual power consumption in non-tropical areas will probably be 10 – 20% less than the Star label rating, particularly in the cooler months.
  2. Running an old fridge on a solar system is not a cost effective option. If you are on the grid you can reduce your carbon footprint and power bill by buying a new efficient one – unfortunately at the expense of increasing landfill.
  3. For those living off-grid, LP gas is an option but it is somewhat inconvenient and the annual running cost is around $500
  4. If you are off the grid, your best long term option is either a small/medium 12/24 volt chest fridge or freezer or the most efficient 230 volt model you can buy if you want an upright model over 220 litres.
  5. If you can minimize fridge power usage by:
    • limiting the amount of warm food and drink placed in it, try and keep your groceries and drinks cool on the way home etc
    • keeping an upright fridge full, use water containers, esky coolers etc – these act as a ‘cold sink’, taking up ‘air’ space that would otherwise fall out when you open the door
    • keep the door seals in good condition
    • allow plenty of air circulation around the outside of the fridge.

Cheers from Dave and all the RPC crew.

Dave Lambert (Director)

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We install solar systems in Northern NSW and Southern QLD.


QLD:
Gold Coast (from Coolangatta to Southport), Nerang and Hinterland (Beaudesert) and out West (Warwick, Stanthorpe, Killarney)


NSW:
Northern NSW (Tweed Heads to Yamba, including Evans Head, Byron Bay and Ballina); the Far North Coast Hinterland (Grafton via Lismore to Murwillumbah) and out West (Casino to Tenterfield, including Drake and Tabulam, as well as Woodenbong and Bonalbo)

For larger system we also go up to Brisbane or down to Coffs Harbour and even Glen Innes. Other places by arrangement.