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Mercedes Benz Formula One car
Mercedes Benz Formula One race car. Within two years, teams will have to begin testing engineering solutions to making their sport more energy efficient, using technologies that can be applied to road cars in the future. One emerging strategy is the utilization of what the author classifies as 'surge power units': energy storage devices for electric, hydraulic, gaseous or mechanical power.

Balanced Power

EV World's UK racing correspondent considers the implications of hybrid power to Formula One racing

By Chris Ellis

This is the sequel to the EV World article 'Hybrids Overtake' which forecast that motor racing would become the crucible for testing some of the latest techniques for making road cars more efficient. The FIA featured the article in issue 5 of its online magazine 'Automotive' .

Last week BMW, DC, Ferrari, Honda, Renault and Toyota all agreed with the FIA to 'come out with a regulation before the end of this year' covering 'energy-recovery and reuse from braking. That will come in 2009'. Consequently these new hybrid race cars must begin track testing in only two years time. (see www.fia.com) The deadline for agreement on the new regulation is December 31, 2006, which effectively leaves only five weeks now to get it right. The manufacturers and the FIA also agreed to 'prepare draft regulations for devices to use waste heat and exhaust gases to assist the engines in propelling the cars', possibly for implementation as early as the 2010 season. This article reviews the key issues which now need addressing as soon as practicable, because they will set the direction for the details that must be thrashed out by the end of the year. As important as the developments themselves is the insistence by all parties that only those innovations which will help improve the fuel economy of road cars will be allowed in the race cars, hence their significance for EVWorld readers.

These are arguably the most radical changes in Formula One since it began, so it is almost inevitable that further fine tuning of the regulations will prove necessary as the teams get creative. However, it is in the interests of all the parties that the longer-term objectives are thought through and agreed, so that an initial technical direction can be set which won't require major corrections later.

The levels of g force experienced in F1 during cornering and braking are closing fast on the limits the human body can stand without the aid of g suits and special controls. Assuming these aids remain forbidden, only during acceleration is there scope for significant improvement in performance. The theoretically ideal enhancement would allow an increase in acceleration while avoiding an increase in downforce and consequent cornering speeds, and would also demand additional driving skills in handling the extra power and knowing when to apply it.

The FIA has already predicted that most road vehicles will eventually be fitted with units which recover and reuse braking energy, a view that the Chairman of Toyota has also publicly expressed. Irrespective of whether the energy initially fed into the vehicle is in the form of a gas, a liquid or electricity, there will be an increasing need to recover and reuse braking energy to help save fuel, often referred to as regenerative braking. In this article, the unit that collects braking energy, stores it temporarily and later helps deliver a surge of additional power is referred to as a surge power unit. To maximize efficiency, a surge power unit is required whether a road vehicle uses a conventional petrol or diesel engine, a fuel cell, a gas turbine, or even a battery. The surge power unit can also provide a temporary storage system for energy recovered from sources other than the brakes. For example, some or all of the energy recovered from the exhaust system could be fed into the surge power unit, rather than straight back into the engine.

Most exhaust energy recovery systems developed for road vehicles run optimally when the truck or car is traveling at a steady cruising speed and a constant flow of exhaust energy is available. In a typical example, steam is superheated in a heat exchanger integrated with the exhaust system and is run through an expander which applies additional torque to the engine's crankshaft or transmission. The waste steam is then recycled through a condenser and returned to the heat exchanger. Now consider what happens to a road car in city traffic. The average amount of heat is low, and the peaks of strong heat output are during brief bursts of acceleration. However, there are inherently a few seconds of delay while the exhaust system heats up, so peak steam generation is often reached just as acceleration is no longer needed, and during initial acceleration the steam system contributes very little extra power. The remedy is some form of energy store, which could involve increased thermal capacity or installing a pressure vessel, but this implies extra weight. However, if a surge power unit is already fitted, extra energy capacity may already be available, at little or no weight penalty. There may be considerable gains in efficiency from feeding some or all of the energy recovered from the exhausts into the surge power unit rather than the engine, as well as some advantages in controlling the extra power output, particularly in a racing car. In particular, a steam turbine might be directly mounted on a rotor shaft of a kinetic energy surge power unit.

Kinetic energy from the high speed of the exhaust gases is another potential source of increased power and efficiency. One recovery technique used historically on aircraft piston engines and currently on large trucks is turbocompounding. Essentially this uses a device similar to a turbocharger, but without a compressor. Instead, the turbine is usually geared directly to the crankshaft, feeding the kinetic energy from the exhaust back into the engine. However, the teams first choice is likely to be conventional turbo-chargers, with appropriately downsized engines. As we will soon see with road cars, the ideal combination of power and efficiency is a downsized engine combined with a 'strong' surge power unit. Another possibility is to feed some of the energy from the exhaust turbine(s) directly into the rotors of a kinetic energy surge power unit.

The FIA has already said that it would be 'quite happy' to allow the front wheels to be used to recover and reuse braking energy, and this will be increasingly attractive as the surge power units become more powerful. Given the extra power potentially available from the exhaust energy recovery systems, the enhanced traction of four wheel drive will become increasingly necessary, although it will inevitably come with a weight penalty.

Several journalists have suggested that the new energy recovery systems will be used to increase performance rather than cut fuel consumption, but this almost certainly misunderstands the FIA's intent and resolve. Here's the sort of problem the FIA is facing, with one possible solution. Next year, 'functionally stabilised' engines may be producing nearly 800 bhp, with more to come when they begin to run on biofuel blends in 2008. The FIA already anticipates that some teams will be able to get as much as 120 bhp out of their surge power units by the end of 2009. By 2011 that might rise to over 300 bhp of surge power. Now add some 80 to 120 bhp recovered from the exhaust system. As a result, the peak combined output of the car's power units could easily approach 1,100 bhp by late 2009, with an average energy output equivalent to a conventional engine with almost a thousand horsepower. Left unchecked, this would inevitably lead to significantly faster cornering speeds, a result the FIA definitely does not want.

The FIA and all the players are committed to maintaining Formula One at the pinnacle of motor sport, and a practical definition might be that no other cars can get round an F1 track faster. But that doesn't mean Formula One has to be as fast as any new technology permits. In fact, many of the current regulations are already set to prevent precisely that. The FIA, with the sometimes grudging agreement of the teams, has over the years and on several occasions pulled peak power back to well under the thousand horsepower mark, principally by reducing the effective maximum engine capacity. The FIA has said that it wants a fuel flow limit for 2011, rather than an engine capacity limit. So let's assume that the FIA and the teams would like to see the 2011 cars setting only slightly better lap times than were achieved in 2006, but with a fuel consumption improvement of, say, 40%. What might the 'balance of power' be like if the new engine regulations for 2011 were set with that basic objective, but in the context of the new energy recovery systems?

For the sake of discussion, several numbers are offered here which are still too approximate to dignify at this early stage as predictions or forecasts, but hopefully they should serve to explain how it will be possible to keep Formula One as fast as ever and make the racing even more exciting with more overtaking, yet still achieve the 'relevance' objective of a radical reduction in fuel consumption agreed by the manufacturers and the FIA. Let's assume that engine power alone is effectively cut to some 600 bhp by 2011, to which can be added almost 100 bhp of exhaust energy recovery. Assume also that the peak rating of the 2011 surge power units is about 300 bhp on braking and acceleration, with an energy storage capacity that allows peak acceleration for up to 6 seconds. Because sustained peak power is now only some 700 bhp, downforce will probably need to be lower, to reduce drag in an attempt to maintain top end performance. However, accelerative power out of some corners will still approach 1,000 bhp. The 2011 cars should be significantly quicker accelerating between, say, 100 and 180 mph than today's cars. On balance, lap times should remain very similar, but the net input of energy (i.e. fuel) should be significantly less, and the beneficial effects of the new systems will be clear, particularly if the 2011 regulations properly reward good fuel economy.

Now let's get back to the initial proposals for 2009. The FIA has proposed a maximum weight limit of 20 kg for the surge power unit, presumably to place an (initial?) limit on the extra power and energy available. This cautious approach has some advantages, but there are potential problems in setting a maximum weight limit for the surge power unit. There is the distinct possibility, during the first season at least, that the 'baby' surge power units may prove less powerful and usable than desired, and won't be able to provide the strong surges of acceleration required to increase overtaking. In other words, weight-limited regenerative braking could prove a damp squib, at least initially.

Now consider why there is a minimum limit on the total weight of the car and driver of 550 kg (by 2008). It's essentially to limit costs and to ensure safety is not compromised by pushing the technologies too hard. There is a similar minimum limit of 95 kg on the engine. Putting a maximum weight limit on the surge power unit would seem to run counter to this sensible and well-accepted approach. Here's a more attractive alternative: note that this is not a proposal for a regulation, merely a demonstration that the FIA's initial suggestion is probably sub-optimal. What if the minimum weight of the surge power unit were to be set at 30 kg, say, and the minimum total weight of the car and driver has to be 550 kg plus the weight of the surge power unit? Amongst other possibilities, this might allow the 'poorer' teams to run 2008 spec non-hybrids quite competitively in 2009 until their richer brethren had demonstrated the net advantages of the slightly heavier but substantially more powerful 2009 spec surge power cars. If the FIA holds to the view that surge power units must be available to other teams (with a price cap), this would set up an open and competitive market where the buyers would be able to assess the relative advantages of the alternatives on the race track before committing themselves.

Of course, this might result in the peak combined power of some cars approaching 1000 bhp by 2010. However, bear in mind this would only be for brief periods, while surge power is invoked. The top speeds would be determined by 'only' 800 bhp, as would most other speeds most of the time. But imagine a surge power unit with a peak power rating on braking and accelerating of, say, 400 bhp (300 kW) and an available energy capacity of 500 Wh. Suppose this can be achieved within a weight budget of 50 kg. Early indications are that this performance envelope might be available by 2011, when the new engine regulations are due. Consider that a 200 mph down to 80 mph braking event might take 2.8 seconds, sufficient time for the surge power unit to fill from near zero to some 250 Wh. The driver now has at least two seconds of 400 bhp to add to the engine power, accelerating out of the corner, or four seconds at 100 rising to 300 bhp if he has control over the power output of the surge power unit, given that traction will probably be the limiting factor at low speeds with a peak of 1,200 bhp available. Extra skill will definitely be required, potentially delivering more excitement as a result of more overtaking. Note that 'electronics' is no longer a dirty word. Thankfully the manufacturers have prevailed on the FIA to allow advanced electronics to take up its proper role in racing, helping the drivers to keep all this new-fangled kit under control!

New engine rules will be introduced for the 2011 season which will encourage and reward overall fuel efficiency. Clearly these rules can't be set in isolation from the surge power unit regulation, because the key fact is that there will now be three power systems involved, not just the traditional two. The most powerful system will still be the conventional brakes. The maximum power of the braking system will remain limited by traction at maximum speed and downforce, at over 2,500 bhp from maximum speed with a 2006 spec car. The energy acquired by the surge power unit is a function of the braking time as well as the power, so it is in the interests of extra acceleration that braking times are longer. A key objective is to make Formula One more exciting by enabling more overtaking. Another is to highlight the relative skills of the drivers, rather than hide them behind the technology. It has been well-argued that lengthening braking times should allow more overtaking, and the resulting extra energy from regenerative braking may allow drivers increased scope to show off their tactical skills in choosing when to invoke surge power.

This all argues for the FIA to use its new control over maximum engine speed as a simple and easily monitored means of limiting maximum combined power and ensuring that overall safety is not impaired. A suggestion: leave the 19,000 rpm limit in place until 2009 as planned, but be prepared to pull it back to around 18,000 rpm or less in 2010, if the extra power from energy recovery exceeds expectations. This might drop engine power to about 700 bhp, but leave total peak power at over 900 bhp if the full range of energy recovery systems are in place. Because of the relationship between top speed, downforce and power, this should then result in a reduction in maximum downforce, with a consequent lengthening of most braking times and the recovery of more braking energy per lap, with more energy for overtaking as a result.

The immediate concern is to ensure that decisions taken in the next month or so don't result in Formula One heading off in a direction which conflicts with the longer term aims. To summarize, the key suggestion is that the additional weight of the energy recovery systems should be added to the 550 kg minimum total weight, rather than maximum weights being set for the units, and that any potential problems from an excess of power beyond 2009 can be met by a reduction in the maximum rpm limit on the engines. This should then result in a relatively smooth transition to the new 'fuel flow' regulations of 2011. The FIA's proposed changes are the most important since Formula One began; let's make sure we get the rules right for a new 'balance of power'.

Times Article Viewed: 14235
Published: 27-Nov-2006

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