> Some time ago I briefly looked into the Aquair online and came away > with the impression that it seemed rather expensive... ....
We have been using one of these turbines for about 6 months now. It is located just on the downstream side of a hole in a wall - at what was formerly the intake of another turbine. The hole being the upper end of the former penstock. The wall on its upstream side creates an intake pond that holds the water level at between 40 cm and 60 cm above the top of the hole depending on the season. The diameter of the hole is 150mm, the diameter of the propellor is 312 mm Here are my first hand observations: 1. The unit is solidly made and well suited to continuous operation. 2. The need for screening depends on the site, but this unit is much less demanding than most other turbines discussed within the group. We do have a broad mesh screen at our site, to stop platypuses from being swept into the path of the blades, but the turbine itself does not need screen protection. 3. Output is approximately 40W with 40cm of water above the hole, rising to 55W with 55cm of water above the hole. 4. The unit produces two equal but independent single phase AC outputs, with frequency depending on RPM. These are rectified to DC using two bridge rectifiers supplied with the unit. In our system the DC outputs are paralleled and fed to the input of an AERL Hydromax controller, that controls the charging of a 12V battery. We have a 24V Aquair UW turbine and have observed that the peak power voltage ranges from about 29VDC at 40W or less, to 36VDC or even 40VDC for outputs of 50W or more. I think it is possible to place the rectified outputs in series, creating in effect a nominal 48V unit. This would be of benefit using a Hydromax [or other DC/DC stepdown controller] to charge a 24V battery - however we have not tried this. 5. The Hydromax controller allows the turbine to be loaded exactly to the peak power point. However, we have repeatedly observed that doing this runs the risk of causing the turbine to "stall" - especially when held at around 29VDC or 30VDC. Output suddenly drops to at most half of what it should be. This can only be reversed by allowing the turbine to speed up by relaxing the load and then re-establishing the maximum power point. For this reason, we run the unit at a little above the peak power voltage. Some comments: 6. In our case the Aquair is a robust, cost effective solution for reasons that will be applicable to any site where: (a) the available head is either non-existent or so low that there is no option other than to place the turbine in the main flow of the stream (b) the site is subject to flooding The beauty of the Aquair is that it will operate unimpeded, so long as water flows through the propellor, regardless of whether the turbine is barely covered by the spray it creates or is under three or more metres of water because of flooding. It is not particularly efficient, having a water to wire efficiency of about 15% to 20% compared to 40% to 60% for other turbines commonly discussed in this group. However, it is easy to install and will work in conditions where other types of turbines don't stand a chance. 7. It may appear that output will be increased by increasing the diameter of the hole to match the diameter of the propellor. However, doing this will cause the water level to drop, resulting in both increased air being drawn in through the hole and reduced water velocity at the blades. The hydraulics are site specific and complex - at our site I have no desire to increase the diameter of the hole beyond its present 160mm. Regards, Max Enfield Planetary Power ------------------------ Yahoo! Groups Sponsor --------------------~--> $9.95 domain names from Yahoo!. Register anything. http://us.click.yahoo.com/J8kdrA/y20IAA/yQLSAA/FGYolB/TM --------------------------------------------------------------------~-> Does your company feature in the microhydro business directory at http://microhydropower.net/directory ? If not, please register free of charge and be exposed to the microhydro community world wide! NOTE: The advertisements in this email are added by Yahoogroups who provides us with free email group services. The microhydro-group does not endorse products or support the advertisements in any way. More information on micro hydropower at http://microhydropower.net To unsubscribe: send empty message to [EMAIL PROTECTED] Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/microhydro/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
