One of the technologies that caught my eye at the recent AFCOM show is the Coolair or TACAS system from Active Power. This DC power source operates on compressed air that turns a high speed turbine. The idea is that this device will replace the VRLA or wet cell battery systems for your 3 phase UPS. Active Power claims that this device will be more reliable, better for the environment and cheaper to maintain and own than batteries. See the link below for more details.
Interesting idea but I haven't seen it in person. Looks like it uses bottled gas? Did it have an on-board compressor? Doesn't look like it. If not, I wouldn't want to have to refill bottles to maintain backup power readiness. Batteries recharge once the utility returns.
The system uses compressed air. I asked about an onboard compressor too. It turns out that it does in fact have one. In fact, the refill time for the bottles is typically much lower than the recharge time for batteries.
In general most of those designs don't include an air compressor to fill up the tanks. The idea is that you can have a 3rd party deal with refilling your tanks and it cuts down on the cost of the unit. My biggest problem with the design is two part. First, you don't have ready to go power at second 0. With batteries, when there is a need, the supply is ready. With any sort of turbine system, you need something to spin up to generate power, and what will carry the load durring that time. My second problem is the solution to the first. To carry the load during starup times, you usually have a flywheel of some sort. Not a bad answer, but now you have all the mechanical problems/risks of a turbine, and a flywheel system.
I personally have become a big fan of the Pentadyne/Liebert fly wheel system in line with battery chains. If you lose power, the fly wheel takes the big hit of the entire load of your facility while the generator starts up. If setup right, the generator will be on and taking the load of your facility before the UPS's drain the flywheel. If for some reason it takes a little longer (cold start in the winter etc...) the batteries get a nice slow ramp up on the current draw as the fly wheel spins down. Best part about their fly wheel is that it has a 3 minute recharge time so your ready to go before the generator has even cooled down.
Grahn,
The Active Power Solution is very new and as a result many people do not know how it works. Let me address your concerns with the design of this system. First, this system absolutely provides power at second 0. Just as you suspected, the spin-up-time problem is solved using an internal flywheel that provides power as the turbine comes up to speed. This flywheel operates in precisely the same way as the Pentadyne system that your reference. The flywheel takes the majority of the hit on a loss of power while the turbine comes up to speed. Once the turbine is at speed, it takes over the load in the same way that the batteries take over the load in the Pentadyne system.
Secondly, the Active Power product does have an onboard air compressor. The system is typically recharged at a much faster rate than a battery system is recharged.
Lastly, you stated in your post that the “now you have all the mechanical problems/risks of a turbine, and a flywheel system”. On the contrary, a flywheel/turbine system is much less risky and problematic than a flywheel/battery system. Batteries are, by a very wide margin, the component of any UPS system that is most prone to failure. In addition, batteries are the most maintenance intensive component in the UPS system. This maintenance requirement drives the cost of ownership way up. Thus, batteries always drive the total cost of UPS system up and the reliability down. Clearly if an alternate can be found it should be considered.
Beyond the high expense of purchasing and owning batteries, batteries have the following limitations and hazards:
• Batteries are famously sensitive to changes in temperature. Small increased in temperature can take years of the expected life span of a battery system.
• Batteries can be damaged by deep discharges. Most UPS manufacturers place limitations on the depth of discharge on their battery systems. The battery manufacturers insist on these limitations because they know that a couple of really deep discharges and their batteries are toast. So every UPS system has stored energy that is completely unusable.
• Batteries provide a fire hazard. Thermal runaway is a phenomenon that can cause a string of batteries to melt down like the reactor core at Chernobyl.
• Batteries provide an explosive hazard. The electrochemical reaction that produces electricity in a battery also produces Hydrogen. Hydrogen is wildly hazardous; think Hindenburg (Oh the humanity!)
• Batteries provide an acid hazard. Batteries are full of acid. This acid can leak and harm personnel. At the very least this potential hazard requires the additional expense of spill containments and spill kits.
• Batteries provide an electrical shock hazard. DC power causes muscles to seize resulting in shock victims being unable to free themselves from the voltage source until it is fully discharged.
• The materials used to manufacture batteries damage the environment during the mining process, during the refining process and during the fabrication process.
• Used Batteries are hazardous waste and difficult and expensive to dispose of.
I could go on but I think my point is clear; there are few technologies that are more problematic and risky than the lead acid battery.
The problems and risks associated with batteries are so profound that nearly every UPS manufacturer has been looking for an alternative for years. Flywheels, fuel cells, ultra-capacitors, gas turbines, windmills you name it, have all been tried. (Okay, I’m kidding about the windmills.)
Using compressed air as a stored energy source is an elegant, economical and reliable solution to the problems posed by batteries. The Active Power solution is highly reliable, extremely cost effective, easy to maintain and easily rechargeable. I urge you to check out the website and read the white papers and brochures about the system. I think you will be impressed. I do not work for Active Power or have any formal agreements with them to promote their product. Let me know if you have any questions.
I have requested some more docs from them regarding the turbine. Once I've read that I might have some questions. Biggest things that concern me are the following.
Local Service (How many companies, and how well trained would they be)
Internal Redundancy (Valve sticking, sensor failure, mechanical failure)
Technology behind flywheel design. (vaccum pump vs sealed design)
Pressure problems, tank issues. How do you keep one tank from causing problems with others (slow leak).
Recharge time, power requirements, physical size per minute of run time.
Max KVA/KW rating (was 100kva back when the Idea was announced).
Early detection of impending failure? (Flywheel does one thing constantly, if it dies you know that moment, and hopefully not when it was under load)
What sort of service needs to be done to keep it running in top shape.
If the docs don't cover it, I might see what you know, or contact a rep for info on that.
Those are terrific questions. I am mostly sold on the operational theory of the product. However, I too have questions about the manner in which that theory was implemented, safety features, failure detection and component reliability. In addition, maintenance requirements and service coverage are very valid concerns.
Let us all know what you discover.
Thanks for the input. This is precisely the type of dialog that I hoped for when I posed the question.
ericgallant
The technology that will replace VRLA batteries?
