## Volvo Car Group testing lightweight structural energy storage material applied in trunk lid and plenum cover

##### 17 October 2013
 A composite blend of carbon fibers and polymer resin is being developed that can store and charge more energy faster than conventional batteries can. Volvo Cars is the only car manufacturer participating in the EU-funded project, which started in early 2010. Click to enlarge.

Volvo Car Group—the only automaker participating in a 3.5-year EU-funded project developing a prototype material which can store and discharge electrical energy and which is also strong and lightweight enough to be used for car parts (earlier post)—has created two components for the testing and further development of the technology. These are a trunk lid and a plenum cover, tested within the Volvo S80.

The material combines carbon fibers and a polymer resin, creating a very advanced nanomaterial, and structural supercapacitors. The material can be moulded and formed to fit around the car’s frame in locations such as the door panels, the trunk lid and wheel bowl, substantially saving on space.

In one of the papers related to the work, a team from Imperial College London (the academic lead on the project), noted:

To date, two main strategies have been applied to the fabrication of multifunctional structural energy storage devices. One straightforward approach is a multifunctional structure, physically embedding energy storage devices into conventional fiber-reinforced composites or using structural composite laminates as packaging to protect the devices. Such devices have been reported to operate normally under low mechanical loads. However, this approach offers only modest mass/volume savings and issues such as delamination at the device/ composite interface may be limiting.

An alternative, potentially more beneficial route is to produce truly multifunctional materials, consisting of multifunctional composite constituents that simultaneously and synergistically provide structural and electrochemical energy storage functions. Earlier work has been focused on multifunctional structural batteries and dielectric capacitors. The concept developed in this work is that of multifunctional structural supercapacitor composites, initially focusing specifically on electrical double layer capacitors (EDLCs), but with an obvious possible extension to pseudocapacitor devices, incorporating redox active elements.

—Qian et al., 2013b

As applied in the S80 components, supercapacitors are integrated within the component skin. This material can then be used around the vehicle, replacing existing components, to store and charge energy.

 Close up of the trunk lid carbon fiber composite. Click to enlarge. Placing the structural super capacitor laminates on the outer skin of the trunk lid. Click to enlarge.

The material is recharged and energized by the use of brake energy regeneration in the car or by plugging into the electrical grid. It then transfers the energy to the electric motor which is discharged as it is used around the car.

The breakthrough showed that this material not only charges and stores faster than conventional batteries can, but that it is also strong and pliant.

The trunk lid is a functioning electrically powered storage component and has the potential to replace the standard batteries seen in today’s cars. It is lighter than a standard boot lid, saving on both volume and weight.

The new plenum demonstrates that it can also replace both the rally bar, a strong structural piece that stabilises the car in the front, and the start-stop battery. This saves more than 50% in weight and is powerful enough to supply energy to the car’s 12V system.

Volvo suggests that the complete substitution of an electric car’s existing components with the new material could cut the overall weight by more than 15%. This is not only cost-effective but would also have improvements to the impact on the environment.

 Trunk lid being mounted on to the test vehicle. Click to enlarge. Plenum cover in place. This replaces 3 previous items in a standard car: the rally bar, traditional plenum cover and the start-stop battery, which alone saves more than 50% of system weight. Click to enlarge.

The project included Imperial College London as the academic lead partner along with seven other major participants in addition to Volvo: Swerea Sicomp AB; Bundesanstalt für Materialforschung und-prüfung BAM; ETC Battery and FuelCells; Inasco; Chalmers (Swedish Hybrid Centre); Cytec Industries (prev UMECO/ACG); and Nanocyl.

Resources

• Qian H, Diao H, Shirshova N, et al. (2013a) “Activation of structural carbon fibres for potential applications in multifunctional structural supercapacitors”, J Colloid Interface Sci, Vol:395, 0021-9797, Pages:241-248 doi: 10.1016/j.jcis.2012.12.015

• Qian H, Kucernak AR, Greenhalgh ES, et al. (2013b) “Multifunctional structural supercapacitor composites based on carbon aerogel modified high performance carbon fibre fabric”, ACS Appl Mater Interfaces, Vol:5, 1944-8244 doi: 10.1021/am400947j

OK, lets look at what is apparently technically feasible for transport in maybe 2025.

No doubt electric motors will have disappeared into the wheels, or at least just inboard of the wheels to minimise unsprung weight, by then.

This Volvo tech apparently may be able to power the car for ~130km, surely far enough to get them onto induction powered electric highways.

A visitor from the distant past, say around 2010, would be amazed by all these cars, not doubt without drivers, whizzing along with no visible power source!

Now maybe none of this will happen, but there do not seem, so far at least, to be any technical reason they they can't.

Davemart may be closer to near future reality than many think?

Integrating e-storage units into vehicle components may be the way to reduce volume and weight of near future e-vehicles?

Of course near future e-vehicles will have ultra light weight e-motors mounted-integrated in ultra light weight e-storage wheels?

I am extremely skeptical of this being a solution for the future of e.cars. The concept is not new and has already being proposed for mobile phone, use the shell as a battery to save cost and weight and volume. The problem is that the shell of a car is exposed to shock absorption which is certainly not where you want to store energy, also replacement of these parts in case of light accidents would be tremendously costly. I think that storage of energy and frame have too different functions and that is not a good idea to merge them for obvious practical reasons.

A more appropriate study in this case, IMO, would be comparing fuel savings to a car lightweighted with a CF hood and trunk.

E-Car roof, hood, booth cover and all windows could eventually become combo solar panels and e-storage units. Those special window panes could dim (on the inside layer) automatically to reduce energy consumption and increase solar energy recovery.

With a few added high performance batteries it could drive hours, specially on sunny days. Many people living in very sunny places would (almost) never have to plug it in. It would fully charge in open parking places.

Fascinating. What about penetrating objects that could cause a short at the point of penetration? Carbon will burn, after all.

@Nick:
Some battery chemistries resist damage from punctures very well.
Toshiba's lithium titanate for instance had a video released of their driving a nail through it without is causing a fire.

Volvo must be aware of the potential problem, and are presumably reasonably confident that what they are looking at will cope, as it is surely on their testing schedule.

The same thing really applies to Treehugger's comments.
The problems are obvious, and Volvo must feel that they have a reasonable chance of getting around the problem of dual function materials, and perhaps they may add up to more than the sum of the parts.

There are some pretty tall orders in getting a working technology from this though, I would agree, and can only wish Volvo luck in their brave attempt.

The other car makers don't fancy having a go, which perhaps tells us something about the challenges!

I agree that Volvo, if anyone, would be acutely aware of any safety issues, considering their culture and branding.

@HarveyD

A few hard numbers. I took the length and width of a typical mid-size car and came up with a plan area of 7.2 m2. If you made an allowance for windows, you might have 5 m2 of area available space and this is probably extremely generous. I live just north of 40 deg so I need to multiply this by 0.75 (I believe you live north of 45 deg so you would need to multiply by 0.7) so now I have 3.25 m2. If I use solar cells that are 20% efficient (very good commercial cells and yes, NASA has extremely expensive cells that are more than 2 this times this efficient) and a flux of 1 KW/m2, I am have a peak of 750 watts available (about i hp). Now if I average over 24 hours, I need to multiple by 24 hr and divide by about 6 to take into account that the day night and the average sun angle. (I calculated the difference between the peak rating at the new Honda plant in TN and the yearly expected KW hrs and yes, I got just about a factor of 6 -- can not beat physics). Now you have about 3 KWh which might give you a range of 8 to 12 miles as the Chevy Volt gets about 2.5 mile/KWh and the Chevy Spark EV gets about 3.9 mile/KWh but this is a smaller car with less available area. Anyway, I do not think that we will have practical solar powered cars or at least not with the cars carrying the solar cells.

Could it be minimal weight/ cost penalty to add solar cells at this stage to leverage this concept,
Distributed fuse contained segments similar to Earth leakage detection device and battery management chip would manage penetration concerns assuming storage capacity /at high energy is present.

This reminds me of the anti corrosion devices available for vehicles, trailers esp salt affected boat transporters, which operate on 12v boosted(to?.)
These inhibit galvanic reactions by storing a surface charge between the metal base and the paint surface.

While I have no working experience with that but (as with most free market products)testimonials and enthusiastic salespersons are not hard to find. I believe steel buildings have applied similar devices.

And of course sacrificial anodes working on the principle are ubiquitous.

Finally, ~10klm charge range is 30% average drive.
so drive every third day?some of us do or if considering a tow or recovery from discharged battery, simply walk away and return some time later when both driver and vehicle are refreshed.

Of course there would be charge cycle losses to account for but offset by future energy efficiency gains in the near future that suggest overall mileage increases.

Solar cells integrated into all exterior skin including windows need not increase the weight of the vehicle.

The same can be said about other parts and/of combo solar cells/storage that Volvo is working on.

Eventually solar energy, up to 7 to 10 kWh in very sunny places, could be captured and stored for the return trip home after work. The energy for the morning trip would be transferred from the home unit or the grid.

For an area of 5m^2 at 20% efficiency, a 1kW of solar power rating is available. In sunny areas w/ 2000 kWh/kW/year, one will get on average of 5.5 kWh/day of solar energy. This will allow 15-20 mile of driving in a BEV, at 3-4 mile/kWh. In the summer, there will be over~7kWh of energy/day which will provide up to 30 mi of range on solar power and hence can be totally sufficient for most people. In winters, home charging will be required for the AM trip to work.

Thus, in sunny areas, solar powered car is quite feasible and very cost effective, especially with solar power below $1/kW! Installation cost in a car is quite low when done at the factory, and all the electrical hookup is already there! From the above, if installed solar PV will cost$1000 USD for the 1kW of installed power, then, at 2000 kWh/kW/yr over 20 years, the cost per kWh will be 2.5 cents. This, in contrast to 10-15 cents/kWh grid electricity cost in the USA. A very good deal, indeed!

In Europe or Japan, the solar output will be only little above 1000 kWh/kW/yr, so, the cost per kWh of solar energy there will be 4.5-5 cents/kWh. However, Japanese and Europeans pay 20-30 cents/kWh for grid electricity, so the 5 cents/kWh is even a better deal!

Now, for PHEV-20, being able to use solar energy charging during the day at work means no need to plug it in at work, thus allowing for range equal to a PHEV-40 like the Volt without having to carry bulky, heavy and expensive battery pack. No need to have to plug it in twice a day, which can be problem if no plug in receptacle is available at work place.

A PHEV will likely last for over 20 years, due to the fact that the ICE is used only < 1/2 of the time, so enough time to recoup the \$1,000 cost of the PV panels. An ICE engine is worn out after 120-150k miles, while a PHEV can run for twice or three times that much before the ICE will wear out.

So, you're on to something here, Harvey! Someday, all PHEV's will have integrated solar PV's on the body panels facing upward. It's just making a lot economic sense and more convenient for PHEV due to less plugging in required for a PHEV-20. PHEV-20 will be the most practical PEV for the near future due to having a balance between weight and cost and full utilization of the battery pack before calendar life degradation.

Lateral windows + wind shield + rear window can also be equipped with high performance low cost transparent solar panels. Future Solar panels, with directed light waves and wide frequency band will capture up to 50% of the available solar energy.

In the not too distant future. enough solar panels could be integrated into e-vehicles to capture 7 to 10 kWh per day, in sunny areas. Driving to work may be free for many.

Convert a cheap engine generator to run on natural gas. Use it to charge your ev. Use exhaust heat for hot water. Use hot water for house heating, hot tubs and washing and bathing. This is cogeneration. it is the cheapest way to reduce CO2 release. Cogeneration at companies for auto charging is even easier with microturbines for multiple automobiles and large cooling systems can use the heat and surplus electricity. Energy from a large battery bank can be sold for frequency regulation as in V2G or used for fast charging or UPS systems. Driving slower would be cheaper than solar energy and requires no additional equipment. Vehicles that use CNG or Liquid fuels or both are the cheapest way to reduce CO2 from automobiles. Instead of plugging a prius into the electric outlet to charge, plug it into a natural gas outlet and let the engine charge it. And it is ready heated or cooled to take off for work with simple electronic timing. The same with volt. The gas company can supply 100 kW of gas flow to a house without much thought and perhaps no new connection to mains. ..HG..

@sd,

Right on with the analysis of the maximum available daily energy for a "solar car", and why that makes the whole concept extremely limited and with nothing like the range, speed and payload capabilities that people have gotten accustomed to, and will indeed DEMAND.

Too many people just cannot grasp basic physics and the limitations that can easily be deduced from same.

Harvey D is smoking his solar-powered + hydroelectric waterpipe as usual.

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