Various kinds of bacteria can evolve hydrogen from water using the enzyme hydrogenase. The evolution of hydrogen is a key step in bacterial fixation of nitrogen from the atmosphere. Chemists at the Pacific Northwest National Laboratory have developed a synthetic nickel based catalyst for electrolytic hydrogen evolution based on the known structure of hydrogenase. Physorg has published a story about this research and an abstract of a recent publication of the experimental results is available on line. Nickel based catalysts are already used in commercial alkaline water electrolyzers such those produced NEL Hydrogen (formerly a part of Norsk Hydro). The hope of using hydrogenase base catalysts is to speed up the reaction and thus to reduced the amount of electrode material required to produce a given amount of hydrogen. The PNNL group has succeeded in making a fast hydrogen evolution catalyst but the efficiency with which it turns electrical energy into chemical potential energy is low compared to more conventional catalysts. The PNNL group is now focusing on means for making their catalysts more efficient.
Recently the website insideevs.com published a story about an energy storage innovation award won by the company EVgo which is creating a network of fast charging stations for electric vehicles. In cooperation with UC San Diego they set up an electric charging station powered by PV panels on the station sunroof connected to used lithium ion batteries from BMW i3 electric cars.
The story claims that the solar energy falling on the station roof can charge approximately 15 cars per day, but does not say whether this is the yearly average or whether this represents the peak Summer charging rate.
EVgo is planning to open its first 350kW ultra-fast public charging station in June of 2017 in Bakersfield, California. This station will have four 350kW chargers and will also feature a sunroof connected to lithium ion storage batteries.
A casual reader might get the impression that this station will charge vehicles using only the solar energy which falls on the sunroof. However, it is pretty clear that such is not the case. The capital expense of these high power chargers will not be justified by charging a few tens of cars a day. Nor will customers be happy about their ability to charge up depending upon how many cars happened to use the station in the previous few hours. Including solar panels and used EV batteries may save some amount carbon emissions, but clearly the intention is to hook up this station to the grid and have year round day and night service.
A 100% solar powered transportation system will require a lot more solar panels than can be included on the sunroofs of charging stations. It will also require some means of dealing with long term variations (e.g. seasonal variations due to the the tilt of the earth’s axis and long term variations in cloud cover) in the solar energy flux. Insofar as the costs of lithium ion battery storage are driven down by a cycle life measured in the thousands, they are not a practical tool for dealing solar flux variations on these long time scales.
rogerkb at energyevolutionjournal dot com
Most discussions of electrifying our transportation system avoid discussing the category of heaven duty machinery which has very high fuel demands which makes the lower energy density of batteries look very unattractive relative to diesel fuel. In the long run we need an alternative to diesel. Even bio-diesel is probably sustainable only at consumption levels much below current usage. A Finnish company called Visedo is producing electric drive trains for construction, agricultural, forest and other off-highway machinery based on electric motors which use synchronous reluctance assisted permanent magnet technology (SRPM). Visedo claims that SRPM motors offer smaller dimenson, lower weight, and higher efficiency compare to tradition induction motor (IM) or permanent magnet motor (PM). Heavy off road machinery is typically powered from from diesel engines which both drive the wheels and run various kinds of machinery for lifting, crushing, chipping, etc. The processing machinery is often run through a hydraulic drive train which requires very high power. Diesel engines are often slow to react to these fast-changing demands in power, and they therefore commonly run on high revolutions in order to be able to provide the needed power to the hydraulics. Visedo SRPM motors which which can supply maximum torque in millisecond even from zero speed allows much more efficient use of energy. Visedo’s SRPM motors are extremely rugged and can hold up to the high vibration environment typical of off road processing machinery. The image below shows hybrid stone crusher powered by a Visedo electric drive train in operation:
Visedo typically builds serial hybrid system in which a diesel engine running at a near constant speed turns a generator, which charges up a bank of super capacitors, which then drive the electric motor. The super capacitors are also charged from regenerative braking of the wheels and of the processing machinery. The fuel savings of the hybrid system are quite large and in some cases are nearly 50%. The heavy duty machines which use the diesel engines are huge fuel gobblers so that the extra expense of these hybrid drive trains can pay for itself in a period of 1 to 3 years.
In the case of a hybrid stone crusher designed by Visedo and a stone crushing and recycling company called Rockster the hybrid machine not only saves fuel, but also increases productivity by 40% because of superior handling capabilities compared to the diesel/hydraulic version of the same machine.
Unfortunately, hybrid machine’s which merely cut diesel fuel use in the range of 10% to 50% is not a long term solution to the problem of either climate change or fossil fuel depletion. In the long run (or perhaps even the short run if the worst case scenarios of climate change consequences come to pass) diesel fuel made from fossil hydrocarbons has to be eliminated. In the case of heavy machinery operating near the transmission grid battery electric machines are technically possible, though at present high battery costs and the high required frequency of recharging make them economically unattractive relative to diesel powered machinery. Continued improvement in battery costs and energy density could eventually change this situation.
For true off road application of heavy machinery which are relatively far from the grid another solution will be required. One possibility is fuel cells operating off of carbon emission free hydrogen (or possibly ammonia). One does not necessarily need a fuel cell in each machine to make this option work. You could potentially take a large solid oxide fuel cell and tank full of hydrogen or ammonia to your remote site and recharge the battery powered vehicles using the fuel cell. Again such an option is almost undoubtedly economically inferior to diesel machines at current oil prices, but it at least represent a route to technical feasibility of such off road operations in a post fossil fuel world.
Visedo is also producing hybrid drive trains for transportation applications, but not for passenger cars. Instead they are concentrating on application requiring high power such as hybrid buses and marine transport. I am guessing that in the passenger car power range Visedo electric motors are more expensive than more traditional designs, but offer advantages for high power applications which make them competitive.
rogerkb at energyevolutionjournal dot com
I recently stumbled on the website of a company called Stratosolar which is proposing to deploy floating PV platforms 20km above the earth’s surface. The platforms would be 300 meters in length (along the direction of wind flow) and would be tethered to the ground by kevlar straps. Power cables which would conduct solar generated electricity to the ground would be attached to the kevlar straps. StratoSolar claims that the maximum wind speed of 50m/s at 20km altitude will allow stable, secure floating platform deployment with only small variation is horizontal position (According to their caclulation a length of 300 meters is required to achieve this stability.). Weights would be added to the tethers as a form of gravity energy storage. At 20Km of altitude each kg of weight would store 54Wh of gravitational potential energy (compare 38wh/kg for lead acid batteries). Excess electricity would be used to elevate the weights into the stratosphere, and the descending weights would be used to generate electricity during during period of low PV electricity production.
Twenty kilometers is above the cloud deck as well as being above a large portion of the atmosphere. These two effect lead to larger average incident radiation. StratoSolar claims that their designed deployments will produce three times as much electricity per unit area of deployment. All other things being equal this extra production would translate into one third lower cost of electricity production. However, it is far from clear that all other things are equal for stratospheric PV platform deployment. StratoSolar mention that the platforms could be filled with either helium or hydrogen. Helium would probably be used for inititial deployments, but StratoSolar admits bringing a high energy lifestyles to nine billion people (and this option seems to be the universal goal of climate change techno-fixers) would require the use of hydrogen as a buoyancy gas. There are very significant safety concerns with this use of such a highly flammable gas, but on their FAQ page StratoSolar claims that the engineering problems of hydrogen safety are solvable.
Siting PV panel above the clouds leads to high predictability of electricity production profiles which would lower the need for energy storage and which would make demand management schemes which try to match electricity use to the natural production profile easier to carry out. Furthermore this high predictability of solar electricity output can be achieved anywhere, including locations close to areas of high human population because the variable of cloud cover has been eliminated.
Since the power cables travel through all levels of the atmosphere below 20km the issue of lightning protection is very important. The design of the lighting protection system is discussed on the FAQ page
Whether or not the proposed energy storage in elevated weights is immune to weather is less clear. The weights will be moving through the troposphere which have potentially experience much higher winds than the height where the floating platforms will resides. The robustness of this energy storage scheme in the presence of violent wind is not clear.
Floating PV platforms will cast a shadow on the earth. The shadow will not be in fixed position during the day, and the path of the shadow will vary with the season. StratoSolar seems to to feel that landowners will not mind the relatively small amount of time that shadows from these platforms fall on their land. Whether or not such tolerance will apply in practice remains to be seen.
StratoSolar claims that their proposed solar energy production and storage scheme solves all of the problems associated with solar energy variability. This claim is not true since the seasonal variation of solar influx requires a scale of energy storage which larger than can be achieved by the proposed gravity energy storage scheme.
As far as I can tell from StratoSolar’s website they have not progressed beyond papers studies to real engineering on this PV deployment concept. While the ideas of stratospheric floating PV platforms is intriguing, I am not holding my breath waiting for a real world installation of one of these platforms.