by Luis de Sousa
Tue Jan 24th, 2012 at 03:59:10 PM EST
Last week I went to Longwy's university campus, the Institut Universitaire de Technologie (part of the University of Lorraine), for a conference on renewable energies and energy efficiency. It was an event integrated in an InterReg project for innovation, called Tigre, gathering institutions from Lorraine, Saarland, Luxembourg and Wallonie. It kicked off with a session on Tri-generation, and went on with parallel sessions on waste Biomass and on Hydrogen and Fuel Cells. I opted for the later, feeling really curious on the present state of research on this field.
Cesare Marchetti proposed hydrogen (H2) as a large scale energy vector almost fifty years ago. Then the concern was mainly to find a simple enough way to feed transport systems with what seemed to be a fountain of energy about to come from the expanding Nuclear park. The Nuclear dream is largely gone, but hydrogen lives on. Is it about to come true as a piece in the transition puzzle to a post-fossil fuel world? That's what I was expecting to know.
Today the hydrogen dream is very different from Marchetti's. It starts with a home, self-reliant, grid-disconnected, housing micro-generation systems, mostly solar and wind, that primarily feed the electrical system. Then surplus energy is converted into hydrogen and stored in a container in special division of the house. This hydrogen can later be used to generate electricity through a fuel cell when the micro-systems do not match the instantaneous power needs; the waste heat generated by the fuel cell can also be used to heat the house. Finally this hydrogen can be used to feed one or more vehicles powered by fuel cells. A general presentation along these lines opened the session by the hand of Sophie Didierjean from the University of Lorraine.
There is an obvious philosophical dimension to this dream, that I wont explore here, for technical aspects are enough to question it. This dream is in a way an attempt to save Suburbia in the US, that was successfully exported to Europe. It happens that here Suburbia is rather the exception than the norm, in Europe suburbs are synonym of cheap vertical housing, where most folk park their vehicles in the streets and commute by mass transit.
There is then another important issue, which is financing. For a new house this technology pipeline can easily increase costs by 50%, on a rough estimate, to which adds the increased cost of vehicles. These cost increases translate themselves into higher debt levels that with present day interest rates can be a killer. For grid connected solutions we have feed-in tariffs that anticipate financial returns and offload investor risk, but for disconnected solutions this isn't the case. The case can be posed for directed subsidies to the acquisition of disconnected technologies, but it misses the social contract the feed-in tariffs force, guaranteeing that micro-producers are the most effective possible, favouring higher net energy; this is something much harder to accomplish with disconnected solutions. Once again this can easily become a philosophical discussion, should Society finance a system that translates into a detach from it?
Going straight to the crux of the matter, I'll jump to Volker Loos, from the Fachhochschule of Trier, who gave a general presentation on the possibilities of H2 as an energy vector. I'll have to start from the finish, since it was at the Q&A session of this talk that the critical question came from the audience: the efficiency of hydrolysis today. At best this figure can approach 80% for a water temperature between 70 ºC and 80 ºC. Not bad, but the problem is that the process of H2 usage has just begun, after that comes compression, storage in a container, decompression and electrochemical processing through a fuel cell or by combustion. In all these steps there are mass and energy losses that further cut efficiency, the end result is far from mature electrical storage technologies like back pumping in dams or magnetic flywheels, and also from other emerging technologies like large scale compressed air storage.
Another thing worth retaining from this presentation is the idea of injecting H2 generated at renewable energy parks into the natural gas supply grid. If there is a way I can see H2 working out is this, there are only two conversion steps in the process: hydrolysis and combustion, apart from that it is also important that most of the infrastructure is already in place. The idea is quite simple: using the natural gas grid as a large buffer when demand isn't there for the electricity generated by renewables. The obstacles I see to this scheme are in first place the suitability of the grid, designed to transport a considerably heavier molecule (methane) thus perhaps permeable to H2, raising security and efficiency questions. And finally the whole efficiency of the process: assuming best case 80% for hydrolysis, no mass losses and 60% for a combined cycle combustion the end result is below 50%.
Finally Volker Loos referred that several auto-makers have plans to introduce fuel cell powered cars in the following years: Mercedes in 2014, Toyota and General Motors in 2015 and Volkswagen in 2020. The price of these cars is at this time estimated to be 20% over that of present day hybrids. To be seen what the impact of the increased demand for platinum will be on these estimates.
And to talk about Platinum was Nathalie Job from the Universiy of Liège, an institution presently doing research on synthetic carbons to produce electron conductors for fuels cells. These conductors should both reduce the rate of platinum used per fuel cell and increase its life time. The details of this work can easily go into electrochemical aspects that are well outside my knowledge realm. A read of this article may help you get a better idea of this research is about.
Nevertheless, one can have an idea of how important this issue is with basic algebra. Platinum is one of a handful of metals known by Men that are denser than gold, found in the crust in about the same abundance of the latter. But it is much harder to find and mine, thus its annual production is about 10% of that of gold, in the order of 200 tones. Every year close to 60 million cars are produced in the world, if all of them required the usage of platinum, those 200 tones would translate into little over 3 grams (about 0.15 cm3) per car; fuels cells require in the order of 0.5 grams of platinum per W of power output. Any massification of fuel cells shall require totally platinum free technology.
Still on the chemical side of things was Yaroslav Filinchuk from the Catholic University of Louvain. He came to present a theoretical concept for the storage of H2 using borohydrides, an highly reactive, porous material, that can store light gases. The basic idea is to use hollow spaces that the molecular structures of these materials create to "lock" inside smaller molecules. The main advantage is the possibility of storing H2 at ambient temperatures, thus avoiding energy losses in compression/decompression or liquefaction/gasification processes. They may also reduce mass losses during storage, but once again my knowledge is thin on the field, so I recommend again a closer reading of a recent article on the subject.
Continuous electrical generation
Ending the session was a host speaker, Angel Scipioni from the IUT, presenting the energy mix of France. It was mostly a generalist address with lots of interesting numbers cast here and there, clearly showing that the largest state of the EU has lagged somewhat behind on the build up of renewable infrastructure (because it has a huge Nuclear park). What struck me was a direct reference to Peak Oil, but in the past tense, as an additional reason for a transition to renewables and H2. Even though acknowledging it, Angel Scipioni seemed not give much importance to it, stating that France had so far copped well with higher petrol and diesel prices. I wonder how spread this sort of view is; in any case a reminder of how long the awareness raising process still has to go.
Angel Scipioni finished his talked quickly explaining a research project presently in place at the IUT. The idea is to combine different renewable energy technologies with H2 generation and storage to build a system capable of continuous electrical generation. The concept uses, for instance, technologies that generate electricity from low speed winds. One day I'd like to see an net energy assessment of such system.
So the Hydrogen dream lives on. Where will these research projects lead? Are all of them in vain? Perhaps not, but hydrogen continuously appears somewhat behind alternative technologies; for a massification of it is use as an energy carrier nothing short of a revolution will do. On many regards huge steps forward will have to come up in order to bring efficiency into a comfortable zone. With several other technologies closing on maturity, there doesn't seem to be much time left. And finally, whenever I reflect upon hydrogen I'm always somewhat baffled on why molecules like ammonia (heavier) or methanol (heavier and less hazardous) aren't preferred as energy carriers.