The other day I was out walking around noon looking at the trees. Some took a lot of damage from the harsh Winter, but almost all have enough leaf area to catch most of the light striking their habit. The average maple around here this time of year is averaging 20 or 30 watts.
To do any sort of work you need access to energy in a useable form. Most of the energy we use, and all of the important energy, comes from the Sun. In its original form it is intermittent and ephemeral. Energy storage is a requirement for life. Green plants figured that out and we wouldn't be here without them. They are machines that use photosynthesis to turn sunlight into storable forms of energy. Mostly carbohydrates - basic fuels.
The first part of the industrial revolution was fueled by coal giving easy access to millions of years worth of stored plant energy. Chemical energy was turned into heat which was turned into mechanical energy. The cost of power dropped dramatically and power levels steadily increased creating a revolution, but the work you did had to be close to close to the coal burning engine. In the last 1800s a radical change was introduced - the generation of electricity at industrial scales. Now the mechanical energy from the steam engine was transformed into electrical energy which was transmitted great distances to an electric motor which turned the electrical energy back into mechanical energy or into light.1
Electric light was the killer application early on, although remotely located motors were also desirable. An electric grid grew and spread through the country, but it couldn't go everywhere. Mobility is a serious problem.
One solution for portable electric power was the chemical battery. They turn stored chemical energy into electricity and come in two flavors - primary and secondary.
Primary batteries are not rechargeable. The best AA cells provide can provide about 1.4 watt-hours of energy. Three of them would supply about eighty percent of the energy an iPhone stores in a charge - you might be able to make it through a day on a set. They retail for about a dollar each, so you're looking at about a thousand dollars a year to power your cellphone with them. About $700 per kWh .. 5,000 times the average residential electric rate.. OK for low drain devices like smoke detectors and infrequently used flashlights, but the modern smartphone wouldn't be possible without a different type of battery.
Secondary batteries are rechargeable. They tend to cost more initially and have lower performance for a given chemistry, but the total energy cost is dramatically less for applications like mobile phones and cars ... we'd still be hand starting cars if only primary batteries existed. One of the reasons why the Bio-Lite stove has been accepted in parts of the developing world is that it generates enough electricity to charge mobilephones.
We've talked about the efficiency of an electric vehicle in the past three posts. Automotive grade batteries are still expensive - a 40 kWh battery that would give 100 to 120 miles of range is roughly $20,000 and needs to be replaced after 1,000 to 2,000 charging cycles.2 Gasoline and diesel fuel have much greater energy densities and the initial costs associated with storing them is very low. Electricity may be cheaper over the length of a car's life, but don't expect widespread use without price reductions and range improvements. You might solve part of the problem if you could quickly charge the battery. What if the energy could be stored like gasoline -- as a fuel?
Enter the fuel cell.
Fuel cells turn a fuel like hydrogen or a hydrocarbon into electricity directly. There are a variety of types, but the most interesting for automotive use combine hydrogen with oxygen in the air poducting electricity directly along with water as a waste product. In theory it sounds ideal. If you can somehow store hydrogen in a car, you should be able to refuel quickly rather than slowly recharge and still use the 80%+ efficiency of an electric drive train.
Unfortunately there are problems that need to be solved. When he was Secretary of Energy, Steven Chu was interviewed by Technology Review:
Technology Review: It used to be thought, five to eight years ago, that hydrogen was the great answer for the future of transportation. The mood has shifted. What have we learned from this?
Steven Chu: I think, well, among some people it hasn’t really shifted. I think there was great enthusiasm in some quarters, but I always was somewhat skeptical of it because, right now, the way we get hydrogen primarily is from reforming [natural] gas. That’s not an ideal source of hydrogen. You’re giving away some of the energy content of natural gas, which is a very valuable fuel. So that’s one problem. The other problem is, if it’s for transportation, we don’t have a good storage mechanism yet. Compressed hydrogen is the best mechanism [but it requires] a large volume. We haven’t figured out how to store it with high density. What else? The fuel cells aren’t there yet, and the distribution infrastructure isn’t there yet. So you have four things that have to happen all at once. And so it always looked like it was going to be [a technology for] the distant future. In order to get significant deployment, you need four significant technological breakthroughs. That makes it unlikely.
… If you need four miracles, that’s unlikely: saints only need three miracles.
Politics being what they are have thrown more money into fuel cell R&D and a few refueling stations have appeared in California and Washington DC, but the miracle level problems remain.
The best automotive fuel cells top out at about 60% efficiency (lower for most operating conditions). That means the overall efficiency of the fuel cell plus the power train of a fuel cell electric car is under 50% - much better than the 25% of the average internal combustion car, but much lower the 80% of a plug-in electric car.
Now to find a hydrogen mine... after all, it is the most common element in the universe. Sadly molecular hydrogen is very rare on earth. You probably made it using electrolysis in science class when you were in school, but the process is very energy intensive and too expensive unless you have a very inexpensive supply of electricity. Industrial hydrogen is usually produced from natural gas and carbon dioxide is given off in the process.
Gaseous hydrogen at atmospheric pressure has a very low density and needs to be compressed or liquified if you want to drive more than out of your driveway. It takes energy to compress and liquify hydrogen and both of these denser forms have their own storage issues. If the hydrogen is produced from natural gas it is possible to do the conversion near or at a filling station, but the infrastructure costs are high (a few million dollars per filling station). You could use electrolysis powered by electricity produced off peak by renewables like wind energy and have a much more environmentally friendly fuel, but the process is inefficient. 3
Finally the price of fuel cells is still very high - Toyota has announced a car will be produced late this year, but these will probably be money losing expensive leases. Early on fuel cell electrics won't attract the well heeled green crowd as their green house gas footprint is larger than a plug-in electric. While it is possible to refuel one in five minutes, that won't matter if the nearest filling station is 1,000 miles away. California is spending a lot of money to make a drive between San Diego and Sacramento possible, but don't expect a rapid build-out nationwide.
There is enthusiasm among some of the major car companies - they see themselves as being able to own and control fuel cell production. The major oil/natural gas companies like the idea as they see this as an infrastructure they can build. Some researchers like it as there are some interesting and difficult problems to solve.
Electrified power trains are inevitable. It will go slowly at first - micro and mild hybrids may be standard in ten years and small car niches will start to grow in five. Eventually we'll see an automotive grade metal-air secondary battery and, if it is cheap enough, the internal combustion car becomes a niche vehicle. It seems very unlikely fuel cells will change the pattern.
But it can be said the battery powered pure electric also has challenges, perhaps miracle level in the short term, too. Range anxiety means the user experience of a car is different for most people. While battery EVs are on a path to a wider spread existance sooner than fuel cell EVs, neither will be a major force in ten years. Beyond that something will happen, but these are very complex and challenging systems interacting with other systems including politics and locations other than the US and Europe.
There are many more questions than answers.
1 I'm ignoring water power .. it was very important throughout the revolution. It is just gravitational potential energy being converted to mechanical energy.
2 Battery costs are dropping and should be about a third of this by 2020. Also there is residual value in a battery that is no longer useful in a car -- they'll be used by utilities to storage energy in the grid.
3 The chart from a talk by Ulf Bossel a few years ago.
Just a tip this time. Soon we'll be seeing high quality fresh fruit. Dry some of it. I cut it into slices (except for blueberries) and spread onto non-stick baking pans. Pop them in a cool over (125°F) with the door slightly ajar to permit steam to escape. Drying times depend on fruit moisture content and slice thickness, but allow at three hours for most fruits. Seal them in airtight containers and you'll have fruit later on in the season for a fraction the price of commercial fruit. Last year I dried about 20 pounds of the blueberries I picked along with cherries, cranberries, peaches and apples. All were excellent.
Ferrets love dried cranberries.