Eestor – Finally Some News
After nearly a year of silence since applying for a patent Eestor has gone public.
Eestor’s announcement of third party verification of some itsperformance claims for their ultracapacitor electrical energy storageunits (EESU) has caused a stir in the electric car field. However,while their deal with Zenn motors has generated much press I find the possible uses outside the car industry much more tantalizing.
Not Just For Cars
This could represent a major change in how we power some portableand remote devices. While the EESU is not designed for consumerelectronics they are ideally suited for applications which currentlyrely on batteries as the primary or secondary power source. These rangefrom remote sensing units to telecommunication repeaters. They evenshow promise as storage devices for the ‘green home’, those either offthe grid or with their own limited power generating systems – such assolar cells.
The exact figures for the watt hours per kilogram (WH/kg) deliveredby Eestor’s EESUs are hard, impossible, to find. Estimates run from 250to 450 WH/kg. By comparison, the familiar lithium ion batteries come inat 150 WH/kg, NiCad at 70 WH/kg and 35WH/kg for lead acid. Heavy andneeding constant maintenance, lead acid batteries are the primarychoice for anyone needing to store electricity. If the price of theEESU can be made competitive, they could change that.
(Watts Hours per kilogram is the power to weight ratio of a batteryor energy system. A power source weighing 1kg with a 250 WH/kg wouldlight a 13 watt compact florescent light for 19 hours.)
Have you every grabbed your laptop or digital camera that youthought was fully charged to find out most of the charge was gone. Allbatteries have internal leakage. One of the parameters verified inthird party testing was leakage. Eestor’s patent claims “the dischargerate of the EESU will be lower than 0.1% per 30 days which isapproximately an order of magnitude lower than the best electrochemicalbattery.” With their light weight and low leakage EESUs may be used asa primary power source, with the units designed to be ’switch out’instead of recharged.
Another characteristic of these devices is the recharge time. Mostof us are familiar with traditional capacitors. Except for the verysmallest capacitors charge time was limited, in part, by the inductancedue to plates and the di-electric being rolled into a cylinder. Thesefew diagrams available online show a stack of plates connected inseries-parallel. This should minimize the inductance, making internalresistance the main restriction to charge time.
Since EESU’s are capacitors, they should have a very fast rechargetimes. Certainly within minutes, probably within seconds for smallerunit. Times for charging a vehcle would be comparable to the time ittakes to ‘fill up the tank’ on a SUV or large truck. Going camping, anEESU would give you considerably more power than battery based powerunit and can be recharged in a few seconds.
Rapid charge times, a recycle life of over 1,000,000 and lowleakage make the EESU a cost effective replacement for lead acidbatteries in many application. BUT WAIT – THERE’S MORE.
While I could not find numbers for the min operating tempature, thepatent claims stability up to 85C. Given the nature of the componentsethylene terephthalate, aluminum powder, and barium titanate one mightexpect the EESUs to operate far below min temperatures for conventionalbatteries.
The EESU is just one of many new technologies with the promise ofdelivering electrical energy. The ‘green factor’ of these technologiesmust always take into account that most of North America’s electricalcome from burning coal. However, as alternate ways of generatingelectricity come on line devices such as the EESU will find more andmore use in delivering energy where it is needed.