With the economy now dominating the headlines both generally and in the US presidential campaign, it is worth pointing out that the business, science, and policy worlds are still thinking hard about energy.

Aimed at reducing both oil dependency and GHG emissions, both the Obama and McCain teams have plans for clean cars, as the New York Times outlines.

Both candidates are in favor of plug-in hybrid cars, and the Times points out that the key to improving the battery-only range of hybrids is, astonishingly enough, the batteries.

Lithium ion, (Li-Ion) batteries are emerging as the most likely way of producing cars that can store electricity directly, whether in all electric vehicles (often called EVs) or in hybrids (some combination of internal combustion engine and electric motor).

Lithium ion batteries are relatively new, having been proposed in the 1970s, developed in the 80s, and first marketed (by Sony) in 1991. This is not much time to get a robust, effective and cheap product, and though the batteries for automotive applications are now much more stable, there remain significant hurdles. By comparison, lead acid batteries were invented in 1859 - the same year as oil was discovered in America.

As many people will know to their annoyance, some lithium ion batteries in laptops had to be recalled because of the danger of their spontaneously igniting or even exploding. This would not be good in a vehicle occupied by humans. Lithium is a highly reactive element, but when designed with other compounds, such as iron and phosphates, the danger of fires and explosions in batteries is said to be removed.

The biggest difficulties facing large-scale deployment of lithium now appear to be price and battery management systems. Li-Ion batteries are more difficult to make than other rechargeable batteries and are, as yet, made in far smaller quantities than other kinds of rechargeable battery. There is considerable effort being made to further improve battery chemistry and stability, to scale up battery production, and to reduce the price.

Battery management systems are critical to the performance and safety of Li-Ion batteries. Li-ion batteries are rather delicate creatures and must be treated like thoroughbred horses.  Specifically, they should not ever be discharged below about 2.5 volts per cell, nor charged at much above 4 volts. The former process can ruin the battery, while the latter can lead to thermal instability, to put it nicely.

Li-ion batteries for vehicles are sufficiently young that as yet, there are not many well tried battery management systems available, and even fewer that are sufficiently open in design that they can easily interface with chargers upstream and electric motor controllers downstream.

There is a further opportunity-problem and that is that li-ion batteries do not normally like to be fast charged. Yet, in order to make electric vehicles maximally efficient, it is necessary to recapture downhill and braking energy as electrical regeneration.

Regeneration can result in very large amounts of power going into the batteries - just what Li-Ion batteries don't like. However, there is an opportunity here: electrochemical capacitors (sometimes called ultra-capacitors) are very pleased to receive extremely large currents (as long as they are designed for it). Furthermore, ultra-capacitors can be cycled millions of times without detriment (just like the small capacitors in a radio).

The obvious thing to do is to combine li-ion batteries with ultra-capacitors - the vehicles would be more efficient and the life of the Li-ion battery could be greatly extended. The main problems are the added initial cost and yet more battery management issues.

However, the technical problems are definitely soluble, especially if we have more open battery and renewable power management systems. Such systems would ideally be part of a much larger movement towards open power control systems, designed to take any kind of renewable energy and apply it to any kind of load, be it storage, immediate use, or storage followed by use.

The electronics to do this are in principle here now, but the protocols and platforms are not. This could be an interesting area for those interested in how to be part of the great new game of renewables without having to bet their shirt on a particular renewable energy generation technology.

Cheap and well controlled li-ion batteries in partnership with ultra-capacitors and renewable electricity can and will make a huge impact on our many transport dilemmas. Will we find the money and will to get there fast enough?