E-News Issue #68
Well Christmas is over and we are all back at it for an exciting year ahead. I look forward over the next year to bring you some interesting news and information about Renewable Energy and some new products as they become available.
We've added several dozen new pages to our website in the last month. Almost all major products have specifications and a picture or sketch on our website. Our Hydro Site Assessment Form, as well as our Power System Sizing and Solar Pumping Forms are available.
The Plasmatronic Regulator Manuals can be downloaded in PDF format. Our hydro and the Glockemann pump manuals still need to be added as well as pics of our smaller items.
We have added a new range of composting toilets to our website. There is a range of styles available to suit the weekend cottage through to a large family home. Help protect our environment today.
People First Network & PrintersOver the last couple of years we have been pleased to supply several solar systems to power up remote email transmitters in the rural areas of the Solomon Islands. It is great to see solar technology used for such worthwhile projects. David Leeming who developed and helped set up these rates has written the following report and request for advice about printers:
People First Network www.peoplefirst.net.sb is a rural development and peace-building project in the Solomon Islands. We aim to provide an affordable, sustainable and community-owned rural communications system for the 85% of islanders who live in remote island communities, almost entirely without telecommunications, and then to help them use the Internet-based network to access and share information - and to participate in the emerging "information Society".
With the extreme cost of satellite access in the Pacific (we are talking 100s of USD per month for a 64kbps connection based on a large number of access points - and 1000s for single installations) and the logistical/security problems associated with relay stations (for VHF and microwave / 802.11) - we have opted initially for an HF email network.
Each community email station has a single laptop, a short-wave radio and HF modem and printer. The stations have committees to manage them and operators to help people send emails and others services (Internet searching via specialised web for mail search tools). They are powered by a single 80W panel. Initially very few people can operate a computer, but as the demand grows we add extra computers and offer basic training and public access to their own emails, etc.
The revenues collected pay for all operations; after set up there are no bills sent to the stations, no per minute charges. The main expense is printer ink. We have been using low-cost Canon bubble jet printers (i.e. S100SP, S200, etc). However, each new order we make, we find the ink cartridge is different, and the latest batch had a very small black ink cartridge. We have tried refill kits but this is proving unreliable when done in situ and the logistics of sending physical items or doing maintenance out at the stations are extreme - you need a week in man cases and the cost in domestic air travel, long open sea canoe crossings, etc, make this sustainability issue quite serious for us.
The other issue is power supply. We are forced to use an inverter for the printer, whereas all other equipment can be powered from the DC solar supply. Inverters are fragile and easily abused, unless you pay a lot of money. We would like to have a printer with a DC supply - or at least an internal power supply with a single CD feed which we can "hard wire" to a DC-DC adaptor specially made locally. However, the Canons use three separate voltages from 3V to 22V and this is awkward to arrange.
SO - THIS IS OUR NEED
1. Can anyone recommend the most efficient printer in terms of cost per printed sheet. Laser printers are OK if they are low cost and have low power consumption (they do not need to be turned on all day - only when needed). The 400Wh we usually get from the 80W panels is usually sufficient. If we have to pay AUD 50 or AUD 100 for a cartridge, then an output of less than 1000 pages at 5% is simply not enough. We should pay more in order to spend less, I suspect.
2. Ideally, one as in the above, which can be hard wired for DC
Thanks to Dave Lambert, our resourceful and very helpful friend and supplier at Rainbow Power for this networking!
230V FridgesWith the summer upon us and with some additional information to hand I have updated this article about using conventional 230V AC fridges on solar systems.
As you know we still recommend 12/24V fridges for solar systems as being considerably more efficient than the 230V ones. Despite their higher cost, we still think it is a cheaper option for residents outside of Queensland. The situation in Queensland might be more ‘line ball’ in that most qualify for a 50% subsidy on their renewable energy equipment.
We have come across problems with two 230V fridge installations (which we did not recommend). Both have to do with the auto start function on some inverters. One customer had a fridge that tripped an internal switch when the inverter went into standby mode. This is apparently a 'brown out' protection device for the grid. Another one of our customers has a fridge that won’t start up when the inverter is in standby mode (with nothing else connected). It would seem that this fridge has some sort of soft start relay that the inverter does not see as a load. So this customer now needs to keep their inverter on run mode all the time, which further adds to the inefficiency of the system.
Peter McCloy encountered a problem with a customer who bought a fridge with automatic defrost. It would not restart after the defrost cycle, despite the fact that the light still went on, and if you left it off for a while it would start again.
These refrigerators use a small heater to defrost but after the defrost cycle do nothing for a while, except for a timer which controls the cycle. This timer does not pull enough current to start the inverter and so the cycle never finishes. However, if you open and close the door enough, each time the door is opened the light trips the inverter and the cycle will eventually finish. Similarly, if you leave it switched off the temperature rises and the machine will start when you turn it back on.
Remedy: have someone disconnect the auto defrost cycle, or leave the inverter on, but preferably don’t buy an auto-defrost model. However, we have also had customers who experienced problems with this 'remedy' as the fridge than iced up excessively (more than an ordinary non auto-defrost fridge). This type of modification may void the manufacturer's warranty.
While I appreciate that some 230V fridges are getting more efficient, we suggest you still think twice before going down this track.
Neil McIntosh pointed out that all chest type fridges use less power than an upright. In the Queensland summer his 160-litre Fischer & Paykel 230V chest freezer (run as a fridge) used 768Wh. The same unit uses 389Wh on 12/24 volts.
I'd also suggest that if you are using a unit designed as a freezer you might, in some cases, need to change the thermostat. Consult your refrigeration mechanic about this.
A few years ago we tested a 220 litre Kelvinator first on 230V (1.85Wh) and then modified it to 12V (0.7kWh). Val Rigoli from Fridge and Solar tested a 140 litre LG model GR-131SSF on 230V (1.36kWh) with a 140 litre 12V Waeco model APR-140RF which used 0.58kWh on 12 volts.
So, to summarise:
FRIDGE SIZE: 12V. kWh / 230V kWh / Difference
140 litre upright: 0.58 / 1.36 / 234%
160 litre chest: 0.39 / 0.77 / 197%
220 litre upright: 0.70 / 1.85 / 264%
These tests were carried out using an inverter with only the fridge on. This introduces another ‘variable’ in any test. Some inverters are more efficient than others and their efficiency may be better if other loads in the house are on at the same time.
However, in general terms we can say that an average 230V fridge will use around double the power of a 12/24V Danfoss compressor type fridge. This will mean that you would need extra solar panels, batteries and inverter capacity. While a government rebate may subsidise these costs, it should be noted that batteries are an ongoing expense and several hundred extra amp hours of batteries aren’t cheap!
To conclude, we suggest that while the 12/24V fridge might cost an extra AUD$1000-$1200, they are still good value if you are going to run a fridge on a solar system!
PS I am aware that there are a few very efficient AC fridges available – these are mostly imported models. Conversely, it is also possible to make even more efficient 12V models if they are manufactured specially for the purpose. Boyd had a 198 l fridge/53 l freezer + 102 l veggie box made for him. It uses 2 Danfoss compressors, and has 75 mm insulation on the fridge and 125 mm for the freezer. Inside temperatures are –20C for the freezer, 4C for fridge and 9C for veggie box. It is using an average of 52Ah per day on 12 volts in 20-40°C ambient temperatures. This superb efficiency comes at a cost – AUD$4730 in fact!
Cheers from Dave and all the RPC crew.
Dave Lambert (Director)
- Issue #92 - 06/12/2005
- Issue #91 - 15/11/2005
- Issue #90 - 20/10/2005
- Issue #89 - 29/09/2005
- Issue #88 - 01/09/2005
- Issue #87 - 29/07/2005
- Issue #86 - 04/07/2005
- Issue #85 - 03/06/2005
- Issue #84 - 05/05/2005
- Issue #83 - 01/04/2005
- Issue #82 - 03/03/2005
- Issue #81 - 23/02/2005
- Issue #80 - 02/02/2005
- Issue #79 - 05/01/2005