What to do about renewable energy overflow?

I just came across an article at The Telegraph titled “Firms paid to shut down wind farms when the wind is blowing”. It illustrates very well recent discussions in which I participated, about the best manner to use and distribute renewable energy.

One of the really interesting threads is on LinkedIn (http://bit.ly/9uuDlw) in the Fuel Cell & Hydrogen group. To make a long story short, the opinion that I support is that the energy should be fed to the Grid as first priority, since that is at present the most efficient and economical manner to distribute it. But at times of overproduction, when the Grid cannot handle additional supply, it should be used to produce fuel – liquid fuel – which is the next alternative to energy distribution (and storage). This ties also very well to the theme of my recent posts (Renewable Energy and Hydrogen).

A glimpse into California's hydrogen reality

Last week took place one of the most important Hydrogen events – the US NHA Hydrogen Conference & Expo.
I came across California governor Arnold Schwarzenegger’s speech at the event, and I recommend you to watch it. Both the speech and the event are eye openers to the evolution pace of this industry and the political and business commitment to the hydrogen economy. And it was not all – I know quite a lot of other industry players who did not attend the event, so was this just the shape of things to come…?

Renewable energy and hydrogen – what are the alternatives?

The last couple of months were very busy and did not leave much place for creative writing. But I learned intensively about the state of the art in hydrogen based energy usage, in particular with automotive and off-grid applications.


One of the hottest debates in automotive is the merits of battery based vehicle compared to other forms (hybrid fuel-electric or hydrogen-electric). In the US we saw a major shift from hydrogen to battery, motivated by the expectations that battery powered vehicles are readily available and the least disruptive in terms of required infrastructure, while hydrogen is more complex technically and requires a new specialized infrastructure (assuming the use of compressed hydrogen as the storage option).

But let’s pause for a moment to look at the energy aspects of those alternatives – after all, that’s what we are trying to get in the first place. Our experience with electronic devices such as mobile phones and cameras made us pretty happy with modern batteries – they are small, lightweight and last hours or days before requiring a recharge. Why not put them in a car?
What we tend to overlook is that those electronic devices also made significant progress in lowering their energy requirements. But when considering a car, it’s another order of magnitude.
A cruising car at 90kmh consumes some 20kWh. Compact sized cars such as the Audi A3 have engines that deliver about 100kW, and for example the range of the BMW series 5 engines extends from 125kW to 270kW. In my camera, I have a tiny 5Wh battery that lasts forever and weighs only 28gr. Using that same technology to store 100kWh in a car would require 560Kg of batteries...
A common metric for state of the art car batteries (supporting over 1000 charge cycles) is a capacity of 120Wh per Kg of battery. Which explains why Nissan’s brand new battery powered car, the Leaf, is rated for a mere 160Km of autonomy.

What about hydrogen? In recent years, we saw quite a few real size tests of hydrogen vehicles. One of the best known is the Honda FCX in California, with 100kW engine, 450Km autonomy and 16 hydrogen filling stations in the Los Angeles area. Looks good, except that the hydrogen tank fills up the trunk of this mid-sized car (the image shows the rear part of the FCX chasis with the tank). While compressed hydrogen offers better energy density than batteries and is a mature and known technology, it has a physical limit – in its most dense form (liquid at near absolute zero), it contains only 2.2kWh (8MJ) per liter of volume; and in the Honda FCX the hydrogen is stored under pressure of 350 bars, containing only 800Wh (2.9MJ) per liter.

Hydrogen being the smallest gas molecule known poses its particular issues. It is a tremendous challenge for sealing (even welded/brazed joints still leak) not to mention any long term storage. A hydrogen leak in the atmosphere is much more dangerous than a natural gas leak due to the energy content (remember the Hindenberg?). The infrastructure requirements for compressed or liquid hydrogen based fuel are huge as well. Also, modern storage tanks for compressed hydrogen are made of carbon fibre, a very strong, light and expensive material...

Does that imply that electrical cars are doomed to low performance and limited autonomy? Not if we find better, more dense methods for storing hydrogen.

One such avenue uses, instead of physical pressure or extremely cold temperature, chemical forces to compress the hydrogen. It is long known that some compounds, called hydrides, bind multiple hydrogen atoms in a density much higher than liquid hydrogen. For example, Lithium Borohydride contains 12kWh/Liter (compared to gasoline with 10kWh/Liter and compressed hydrogen with less than 1kWh/Liter).
Practical research presently attempts to produce liquid fuel which could be used with the present fuel infrastructure, and has reached fuels with a density of 1.3kWh to 2kWh per liter. That's already better than compressed hydrogen and still leaves room for much progress and improvement.
But the use of this type of fuel is not as straight forward as compressed hydrogen, since it requires more manipulations. To obtain the hydrogen you need an on-board a fuel processor which, via a chemical reaction, liberates the hydrogen from the fuel. Additionally, the “spent” fuel has to be retrieved at the fuel station and resent to the “refinery” for regeneration (recharging with hydrogen).

What to make of it? Modern human society has grown accustomed to almost instant results in its daily affaires: fast food, micro-oven meals, high risk financial instruments with fast yields, video on demand, mobile internet and accessibility (blackberry...) are typical examples. Faced with mountig energy costs and pollution, the temptation is high to go for fast solutions. I believe that this is a key factor behind the decision of the current US administration to prioritize battery cars over hydrogen, and compressed hydrogen over chemical hydride solutions.
But if you take the time to look at the fundamentals, the ability to get a fast solution is of marginal value.

What we need is high energy density in a sustainable and renewable fuel, which can be stored and transported safely and conveniently and used whenever and wherever needed. The present state of the art points to stable liquid fuels made of chemical borohydrides as the most convenient alternative: simple and low cost charging, using the current fuel infrastructure for storage and transportation, and simple and low cost on-board processing.

I’m looking forward to your views.

Renewable energy and hydrogen – what's the effective cost of energy?

We have seen in my previous post about hydrogen two main factors that can facilitate the supply and competitiveness of Hydrogen – H2 production, and H2 Storage and Transportation.

At present it takes about 1.5 times energy to produce H2 – meaning that we have to invest 1.5kW in order to obtain 1kW worth of H2. I suspect that the energy investment in obtaining 1kW of Coal or other fossil fuel is not less (in particular when you consider the cost of their being non-renwable). I did some research and found an interesting study by Prof Risto Tarjanne – Competitive Comparison of Electricity Production Alternatives - I copy here the relevant graphic.

What this implies is that Nuclear electricity cost is about 2.4€ç/kWh (3.6$ç), and that instead of wasting power during off-peak hours, we can cleanly produce large amounts of hydrogen from water using electrical energy. But given that the boiling point of hydrogen is cryogenic – at about minus 252.87 °C – it is very difficult and expensive to store it as is. One of the main challenges of the hydrogen economy is to find a way to store H2 in a similar density to that of fossil fuel.

Let’s conclude this post by stating that it should be possible to produce hydrogen without CO2 emissions at an energy cost of about 3.6€ç/kWh, or €1.2 per Kg of emission free hydrogen. In the next post, I’ll tackle the storage and transportation issue.

Renewable energy and hydrogen – what’s bringing them together?

I have been studying recently the hydrogen economy, and I’d like to share the insight I gained.

Taking a different look at energy, we should consider all forms of fuel as energy carriers and all forms of fuel production (whether mining, drilling, via nuclear reaction or solar/wind etc…) as primary energy sources.

Presently, most of our primary energy sources are non renewable, and most of our energy carriers deliver their energy while polluting the environment. What we want for tomorrow is renewable primary energy sources and non-polluting energy carriers, all at a consumer cost similar to the present.

Renewable primary energy sources are usually of a stationary nature – nuclear plants, wind turbines, solar farms or biogas plants. As long as we can directly produce electricity and transport it over wires to stationary consumers (such as households) we’re fine. However, much of the energy we consume is in a mobile setting – automotive and various devices. For these applications, as well as for isolated off-grid location, we need an easily transportable, non-polluting and renewable energy carrier. There is a broad consensus that Hydrogen can be such a carrier, provided we find ways to harness it.

Hydrogen (H2) can be cleanly produced from water with electricity generated by a renewable primary energy source, and when consumed it releases energy while producing clean water. In terms of energy content it is also very attractive: 1Kg of H2 contains the equivalent of 33kWh – compared to about 11kWh contained in the equivalent amount of Diesel fuel – and compared to 0.3kWh in 1Kg of a top battery.

I’ll expand on the practical aspects of hydrogen production, storage and transportation in a subsequent post.

In the meantime, I'm keen to learn about your view on the futur of energy.