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Clean Transport Image Credit: Volvo/ElectriCity

Published on August 29th, 2014 | by James Ayre

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Volvo 7900 Electric Hybrid Coming — Cuts Fuel Consumption & CO2 Emissions Up To 75%

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August 29th, 2014 by  

Volvo’s plug-in 7900 Electric Hybrid bus will be officially launched in September, at the International IAA Commercial Vehicles show in Hanover, Germany, according to recent reports.

The International IAA Commercial Vehicles show will be held from September 25th through October 2nd at the city’s exhibition center.

Image Credit: Volvo/ElectriCity

Image Credit: Volvo/ElectriCity

According to Volvo — as compared against a conventional diesel bus, the plug-in 7900 Electric Hybrid bus uses up to 75% less fuel, with an accompanying drop in CO2 emissions. Overall energy consumption is reduced by somewhere around 60%.

These figures were verified last year via field tests in Gothenburg, Sweden, using the buses. You can find out more about that at the Volvo Buses site.

“Noise is a growing problem in many cities. The noise level near to an Electric Hybrid is 65 decibels, i.e. normal conversation level. The Volvo 7900 Electric Hybrid runs in electric mode in average 70% of the route,” Green Car Congress writes. Of course, that doesn’t compare with the pure-electric BYD bus, but 70% is still a decent percentage for operation on an electric motor.

“The Volvo 7900 Electric Hybrid can run as an electric bus in selected areas, and performs as a hybrid on any route. Charging at end stations takes 6 minutes. The Volvo 7900 Electric Hybrid shares the technology of the well-proven Volvo 7900 Hybrid, securing high uptime and availability.”

As of right now, a fair number of large European cities have expressed interest in the model — most notable of which are the cities of Hamburg, Luxembourg and Stockholm, which have already signed purchase agreements. Large-scale production of the model is expected to begin sometime in early 2016 — presumably with a large roll-out of the model sometime after that in cities across the continent.

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About the Author

's background is predominantly in geopolitics and history, but he has an obsessive interest in pretty much everything. After an early life spent in the Imperial Free City of Dortmund, James followed the river Ruhr to Cofbuokheim, where he attended the University of Astnide. And where he also briefly considered entering the coal mining business. He currently writes for a living, on a broad variety of subjects, ranging from science, to politics, to military history, to renewable energy. You can follow his work on Google+.



  • José DeSouza

    Here′s a kind of hybrid bus perhaps Cleantechnica might like to review: http://www.businova.com/en/home/welcome.html

  • José DeSouza

    I hope I planted a seed here.

    • Bob_Wallace

      Stay on it. See if you can get some data/info that might give us an idea of how practical a hydraulic bus might be.

      You might be able to find a forum on line where engineer types hang out and answer questions for those of us who know little. Someone could probably start with the weight of a light weight bus and the amount of energy reasonably stored in tanks and generate out a rough range estimate very quickly.

      • José DeSouza

        Also hope at least one of these guys is a keen reader of cleantechnica: http://www.altairbusolutions.com/BUS-Images-Videos.aspx

      • José DeSouza

        Here′s an idea similar to mine: http://electricvehicle.ieee.org/2014/02/02/electric-hydraulic-hybrid-drivetrain-for-city-vehicles-a-novel-approach-to-on-board-energy-storage/. Although it should still carry propulsion batteries onboard and the so proposed electric vehicle would be a sort of parallel-configuration HHV rather than a series HHV. An interesting idea, too. As far as I grasped from the article, it could be a regular BEV with the electric motor powering the rear wheels and a hydraulic motor-pump/accumulator-fluid reservoir setup powering the front wheels (actually a FWD vehicle). A Tesla S could be a platform for that; the ‛frunk′ would house the hydraulic propulsion/storage stuff. It would lead to increased complexity for sure, but the trade-off could be less wear and tear to the batteries, a smaller battery bank, the same or longer expected range and less recharging time perhaps.

        • José DeSouza
          • José DeSouza

            Hydraulic propulsion excels at power density whereas electric propulsion excels at energy density: http://www.slideshare.net/fullscreen/kkohlmann/hydraulic-hybrids/3

            That essentially means hydraulics is good for surge starts and to recover braking energy at very high efficiency, but won′t carry you very far because it lacks capacity to store enough energy to keep you moving. Electric propulsion, on the other hand, is a good option to keep things rolling if they′re already in movement because batteries can store far more energy, but like to be discharged gently (and to be charged gently, too). Think of energy as a given amount of water; it can be stored in a bucket (hydraulics) or in a sponge (batteries). You can fill or empty a bucket faster than you can do with a sponge. Buckets of water are good for large amounts of water to be handled fast and sponges are good for the opposite task.

            So the challenge for my proposition of an electrically-powered HHV is how to make that bus be able to make to the next bus stop-recharging station with a relatively small amount of energy stored in the hydraulic accumulator(s), if one doesn′t want to either carry a bank of batteries on board or to rely too much on live wires hanging above.

          • Bob_Wallace

            That’s how I see it. How far could one reasonably go with reasonable sized accumulators.

            That would determine how close the “pumping” stations would have to be placed.

            Five miles? You’re golden.

            One block? Infrastructure cost likely a killer.

          • José DeSouza

            On the other hand (I apologize for not having any hard figures on it yet), one shouldn′t have to be stiff stuck in some kind of either or dilemma. That bus might as well carry a small bank of batteries to do the ‛energy density job′ along the ‛power density job′ carried out by hydraulics. It critically needs both and each of them can be done optimally by each of the methods; costs having to be optimized as well. So that ‛opportunity′ recharging spots could be spaced farther apart, if hydraulic accumulators weren′t good enough for the job, easing the infrastructure cost deployment hurdle. In any case, I don′t think hydraulic hybrid propulsion should be an exclusive domain of ICEs. After all, prime movers can be anything that turn and do useful work. Another interesting take on hydraulic hybrid propulsion: http://www.innas.com/Assets/files/Hydrid%20brochure.pdf

          • José DeSouza

            Here′s an example of a battery-less electric bus which stores energy in capacitors (comparable to hydraulics in their meager ability to store much energy) doing ‛opportunity′ charging along the route: https://www.youtube.com/watch?v=52-HwZIOuaM

          • Bob_Wallace

            Storing in capacitors is more like storing in batteries.

            Capacitors have the advantage of being able to charge faster than batteries. But they have poorer capacity to volume/weight factors.

            Which brings up another issue. How fast could one reasonably pressurize a hydraulic bus compared to charge batteries on one of the bus systems that uses smaller battery banks and charges at but stops?

            At this point hydraulic buses are an idea. Until someone produces at least an engineering study we have no way of telling whether they would be competitive.

          • José DeSouza

            ‟Hydraulic analogy[edit]

            In the hydraulic analogy, a capacitor is analogous to a rubber membrane sealed inside a pipe. This animation illustrates a membrane being repeatedly stretched and un-stretched by the flow of water, which is analogous to a capacitor being repeatedly charged and discharged by the flow of charge.

            In the hydraulic analogy, charge carriers flowing through a wire are analogous to water flowing through a pipe. A capacitor is like a rubber membrane sealed inside a pipe. Water molecules cannot pass through the membrane, but some water can move by stretching the membrane. The analogy clarifies a few aspects of capacitors:

            The current alters the charge on a capacitor, just as the flow of water changes the position of the membrane. More specifically, the effect of an electric current is to increase the charge of one plate of the capacitor, and decrease the charge of the other plate by an equal amount. This is just as when water flow moves the rubber membrane, it increases the amount of water on one side of the membrane, and decreases the amount of water on the other side.

            The more a capacitor is charged, the larger its voltage drop; i.e., the more it “pushes back” against the charging current. This is analogous to the fact that the more a membrane is stretched, the more it pushes back on the water.

            Charge can flow “through” a capacitor even though no individual electron can get from one side to the other. This is analogous to the fact that water can flow through the pipe even though no water molecule can pass through the rubber membrane. Of course, the flow cannot continue in the same direction forever; the capacitor will experience dielectric breakdown, and analogously the membrane will eventually break.

            The capacitance describes how much charge can be stored on one plate of a capacitor for a given “push” (voltage drop). A very stretchy, flexible membrane corresponds to a higher capacitance than a stiff membrane.

            A charged-up capacitor is storing potential energy, analogously to a stretched membrane.″ Source: http://en.wikipedia.org/wiki/Capacitor

  • Cédric

    How can anyone comment on this bus without knowing the economics of it?
    There are two important questions: how much does this technology add to the cost of a bus? And how much money does it save every year?

    If, for instance, the hybrid technology only costs €50k extra and saves €10k per year, it is a no-brainer! There is no use in cutting emissions at a high price when there are so many opportunities to cut emissions in easier and cheaper ways.
    1 kg of CO2 = 1 kg of CO2

    • No way

      Volvo has been part of a study by Swedish universities on the most cost efficient buses from a TCO-perspective. And a hybrid solution with large enough batteries to cover 100% on electricity while using fast charging at bus stations at a certain intervall keeping the bus running on all electricity.

      Second best TCO option was an all electric bus with enough battery to run the daily distance and charge at night.

      Third best was a conventional hybrid.

      Fourth a conventional diesel bus.

      Fifth a bus on biogas.

      This is simplified but the studie were extensive and with total support and integration of Volvo and Scania. So Volvo knows that best for the customers would be a hybrid bus with fast charging that can cover 100% of the route (on a normal day) on electricity.
      Why they insist on a bus with built to not be as cost effective as possible for the customer while it also being the most green alternative is just baffling.

  • JamesWimberley

    Hybrids are a transition technology. Internal combustion engines are mature, little progress can be expected in their costs or performance, and fuel costs will rise, with or without carbon taxes. EV batteries are young and improving fast. How can Volvo expect to compete with BYD’s next bus design, or the one after?

    • José DeSouza

      By doing away with onboard batteries altogether while BYD is working to improve them. But they have to think fast.

  • José DeSouza

    A hydraulic hybrid bus can be lighter, do it better at energy efficiency and be cheaper in the end: http://www.altairbusolutions.com/
    And, if you insist on using electricity to make it even cleaner, you could muse about combining it with another soon to be available technology: http://www.mobility.siemens.com/mobility/global/en/interurban-mobility/road-solutions/electric-powered-hgv-traffic-ehighway/pages/electric-powered-hgv-traffic-ehighway.aspx.

    • No way

      But never get 100% fossil free, or even 75% fossil free for that matter. A hydralic hybrid is a step backward (or maybe rather a step sideways into a dead end) not a step forward.

      • José DeSouza

        What′s the point you′re trying to make? I′ve just posted an option to completely electrify it (the Siemens eHighway concept) above. It would be just a matter of substituting the ICE for an electric motor. From then on it all depends on how clean the grid would be.

        • No way

          And I commented on that saying that a highway system is of no use for a city bus (but a good idea for long distance buses and heavy trucks), but that it’s a good idea if using some of the systems that are used and avaliable already today for city center catanary systems.
          So you had a good suggestion, but for a different kind of bus. And one bad suggestion.

          • José DeSouza

            Just in case you don′t like catenary hanging above or evenSiemens′s eHighway concept, there are other ginger ways to make an electric motor spin inside an electrified hydraulic hybrid bus. For instance: https://www.youtube.com/watch?v=Ag1hcOonlpU

          • José DeSouza

            Another option to make that electric motor spin on board and charge the hydraulic tank(s) instead of recharging electric batteries: https://www.youtube.com/watch?v=zKM8v0Vdasc

          • No way

            How far are you expecting to be driving on the hydraulic tanks alone? 5 km, 10 km, 50 km?
            What benefits do you find in adding that system to an already electrified bus with batteries?
            How do you plan on having an hydraulic hybrid to be driving on 100% renewable energy for all the trip?

          • José DeSouza

            ‟What benefits do you find in adding that system to an already electrified bus with batteries?″

            In a battery-powered electric vehicle you need to convert chemical energy to electricity to mechanical energy and the other way around when doing regenerative braking. In a battery-less electric vehicle you can skip the chemical conversion step, so it′s more efficient, simpler and more durable. A battery-less EV also weighs less, so more passengers can be carried instead of battery bank deadweight. Trolleybuses, for instance, just do it. What I′m proposing is a sort of infrastructure-lean trolleybus system that could be 100% electrically powered, but of a far more flexible variety. It′s possible, as hydraulic hybrids are ‟married″ to a source of motive power, but that need not necessarily be an ICE. And last, but not least, city buses operate far more on a stop and go routine than passenger cars do, so the hydraulic storage/propulsion can be a sensible proposition to that purpose.

            As to your last question, I sincerely apologize for overestimating your intelligence. I should′ve known better; someone who nicknames him/herself ′No way’…

          • No way

            Why didn’t you say that. So what you really wanted to say is that if a city choses a trolley system then you prefer a hydraulic regenerative braking system over a regenerative system using batteries.

            You made it sound like a BEV/PHEV bus vs. a regular diesel bus with only a hydraulic system added. You forgot to tell that you wanted the bus with the hydraulic system to also have a continious power source like a trolley bus.

            And you added some very strange examples which none of them mentioned a trolley bus.

            My last question was not serious. It was rather an attempt to provoke you into explaining how you wanted a fast charging battery bus have the battery replaced with a hydraulic system and still get to it’s next stop without using fossil fuels.

            Haha… you don’t have to apologize. I can assure you that nothing is wrong with my intelligence, there are not many rooms I have walked into where I’m not the most intelligent person.
            Knowledge on the other hand might be lacking in various areas, I have never met a person who doesn’t know more than me in at least one area, no matter their intelligence.

          • José DeSouza

            ‟Knowledge on the other hand might be lacking in various areas,″
            Elementary physics, for starters? If that′s the case, it′s nothing to be ashamed of. You can learn about it, too. See my other post to you about energy conversion below.

          • No way

            No no, not in elementary physics. But the physics need to be put into place in a viable system, economically and even more importantly environmentally.

            Your solution is only good one in one very specific case. Which you had a very hard time specifying. You really do need to work on your presentation skills.
            And even then it will hardly make any sense for the bus manufacturers to develop and implement a system that would be used in very few of the buses manufactured, so unless it was the best option for a wider spectrum of models and uses I can’t imagine it becoming a viable option.

          • José DeSouza

            That seems to be your prolblem: a complete lack of imagination.

          • No way

            If it only would take imagination to get our world fossil free, then I’m sure it would be done by now.. :)

          • José DeSouza

            But without imagination we can′t even get started.;)

          • No way

            Well, when the solutions are already avaliable we need more implementation and production than imagination. :)

          • No way

            No no, not elementary physics. But the physics need to be put in an economical and more importantly environmental system.

            Your solution only works well for one specific scenario, which you really had a hard time specifying. You really need to work on your presentation skills, so that we don’t have to try to read your mind or guess what you really want to say.

            Even for that one specific scenario it’s hardly likely that it would be viable for the bus manufacturers to develop and implement a system that is only used for a very limited number of buses produced.

          • José DeSouza

            I started here: http://www.altairbusolutions.com/pdfs/BUS_Story_Sep2011.pdf. There′s a drawing on the lower right hand corner of the first page showing an ICE connected to a hydraulic pump. Get it?

            What have I been proposing all along?
            Right. Then remove the ICE from that drawing and replace it with an electric motor, so it would run the hydraulic pump and recharge that big tank called accumulator (it really doesn′t care whether it′s recharged by a hydraulic pump powered either by electricity or whatever) whenever regenerative braking was lacking.
            Now, the next step: it would be nice if that electricity could be efficiently collected from a ′lean’ infrastructure (preferably with as few or no catenaries hanging above along the busses pathways), wouldn′t it? That′s why I suggested some ways of doing it in the videos I posted above.
            I haven′t been asking anyone to read my mind in any way, I suppose. I guess you′ve been asking the wrong questions all along.
            And in the end, when you′re trying to change the subject.

          • Bob_Wallace

            I see the sense in what you’re suggesting. There are already buses being tested which have a small battery bank and recharge at bus stops along the way. There’s no reason why electricity couldn’t be used to pump up the hydraulic storage when the bus stopped for passengers as well. And regenerative braking would also work with a hydraulic system.

            It comes down to cost, seems to me. There are at least three unknowns. 1) Comparative cost of a hydraulic vs. battery system. 2) Electricity use per mile. 3) Distance traveled between charges (cost of charge point infrastructure.

          • José DeSouza

            Thx, Bob. It′s always a pleasure to hear from you. Phew!

          • No way

            Now answer Bobs question further down.

          • Bob_Wallace

            In all fairness, that (those) may not be an answerable question(s). (I’m assuming Jose is not a principal in the hydraulic bus company.)

            Hydraulic systems are pretty cheap. Batteries currently aren’t.

          • No way

            You must think it’s strange to suggest a system that is either redundant or based on running on fossil fuels when the bus companies already have systems that are cheaper in TCO than an diesel bus or a regular diesel hybrid which can run entirely on renewable electricity.
            To me it feels like trying to invent the Prius when the car companies are already selling Teslas, Leafs, BMW i3 REx’s and Volts.
            I guess I just don’t have your patience, Bob.

          • Bob_Wallace

            Redundant? Right now we have thousands of fossil fuel buses on roads and we need options for getting rid of them. A hydraulic system is worth a look. It may or may not succeed based on economics, but none of us seem to have found that data so far.

            Heck, we might want to consider flywheel systems. That might be another way to get from charge point to charge point.

            A hydraulic bus, like an battery electric bus, would be as clean as the grid providing the electricity. One of the unanswered questions is the amount of electricity per mile. The system using the least amount of electricity from a <100% renewable grid would be cleaner than the other. (Assuming no differences in manufacturing electricity use.)

          • No way

            A flywheel is also a short term energy storage. It’s basic advantage is efficient braking energy recovery. But its energy to mass ratio makes it not viable for more then helping to get that acceleration back that you “lost” during braking.
            If Jose had some numbers to share it would make things more interesting, now it basically just seems like a fixation.

          • Bob_Wallace

            And your numbers?

            “a system that is either redundant or based on running on fossil fuels when the bus companies already have systems that are cheaper in TCO than an diesel bus or a regular diesel hybrid which can run entirely on renewable electricity.”

            What is your cost basis for the claims you’ve made?

          • No way

            See the study I’ve already linked to further down. Which is a study made in cooperation with Volvo, which makes them very aware of the situation.

          • Bob_Wallace

            The one in Swedish?

            That’s not exactly a lot of help, don’t you think?

          • No way

            http://www.bth.se/fou/forskinfo.nsf/0/5ee2925e367c9962c1257c42005ca9d2/$file/Advancing%20from%20efficiency.pdf

            At least it’s some parts of it. If not then you could always phone a friend or use google translate and hope for the best. :)

          • José DeSouza

            Flywheel buses were actually attempted in Switzerland, but their mass to energy ratios were one of their main drawbacks as you correctly stated. http://en.wikipedia.org/wiki/Gyrobus.

          • No way

            And you know what. Volvo have been testing and are testing hydraulic systems, flywheels (mostly in the form of KERS), hybrids, battery hybrids, pure battery, the ehighway for a highway based catenerie system, inductive charging both stationary and in transit, and lots of different renewable fuels.

            All so that they can satisfy customers wants and needs and to be prepared no matter how the solutions might look like in the end.

          • José DeSouza

            Go to hell, Torquemada!

          • Bob_Wallace

            No way is a ‘glass half empty’ sour puss and seems to go out of his way to piss on progress but let’s avoid calling him names.

            http://cleantechnica.com/cleantechnica-comment-policy/

            (Note: “sour puss” is meant as descriptive, not nominative.)

          • No way

            To be totally fair, I don’t piss on progress. I piss on what I feel is not enough progress. :) Just like I’m pissing on Volvos 75% when they could go 100% straight away easily and with basically no added cost.

          • Bob_Wallace

            To be absolutely honest, you piss on progress rather regularly.

            It seems to come from the lack of understanding that goals are seldom reached in a single step, but a series of shorter steps.

            It’s behavior commonly seen from self-described “progressives” who, while well meaning, seem to have little practical knowledge about how things work in the real world.

            Just because you see a perfect, or almost perfect, solution doesn’t mean that everyone else does. Some take longer to be convinced and need to see smaller steps work before committing to the ‘full Monty’.

            And what is the perfect solution for you likely means that someone else’s ox is going to get gored. People don’t like their ox gored and they push back. The best possible at the moment may be a partial solution, let them heal their ox, and then gore them some more.

          • No way

            Maybe my new mantra should be little progress is also progress. :)

          • Bob_Wallace

            Or “A little progress plus a little more progress adds up to big progress”.

          • No way

            Now you’re pushing it. ;) One step at a time.

          • Bob_Wallace

            You mean you don’t wish to be held to the ‘No way – all or nothing’ standard?

          • No way

            A wise old man once said “Some take longer to be convinced and need to see smaller steps work before committing to the ‘full Monty’.”
            Sometimes that applies to me too. :)

          • No way

            How sweet of you :) And very mature ;)

          • Bob_Wallace

            OK, that’s your free shot.

            Let’s see if we can at least pretend to be grownups.

          • No way

            I thought that was a very friendly response. Especially since Torquemada is a pretty serious insult.

          • José DeSouza

            Then stop behaving like someone from the old Spanish inquisition. I′ve been trying to put forth an innovative idea up for discussion so far. Whether it works or not is anyone′s guess. I′ve already posted the links to back up my ideas. What do you want me to do? To read them for you?

          • No way

            Next time I’ll know that you’re a visionary and not full of facts and figures, less substance and more imagination. Then I can adapt my approach to that and look at the vision instead.

          • Bob_Wallace

            OK, guys.

            I’m tired of opening new comments just to see people sniping at each other. Cut it out or I’ll close the thread.

            We’ve all had enough fun for now….

          • No way

            So you want catenaries, a battery and a hydraulic system to get a potentially fossil free bus?

          • José DeSouza

            Jesus Christ!

          • No way

            So from a page with a hybrid bus taking proud in not using electricity and comparing itself to a regular diesel bus I should have made the jump to a catenarie electric system?

            The wrong questions you say. How about this. How do you propose to make a bus with a hydraulic system fossil free without a catenerie system or with one that is only covering parts of the routes?

          • José DeSouza

            By switching the electric motor powering the hydraulic pump to recharge the accumulator tank (if necessary), which, on its turn, will power a pump

          • No way

            And how far can you drive by just the energy stored in that accumulator tank?

          • Bob_Wallace

            It would depend on the size of the tanks, would it not?

            BTW, I did find a site that said regenerative braking with a hydraulic system is about 3x as efficient as a battery/electricity system.

          • José DeSouza

            That′s what one expects to be because of the fewer energy conversions involved.

          • Bob_Wallace

            You just pressurize the hydraulic tanks at some portion of stops along the bus route.

            Here’s the battery version…

            http://cleantechnica.com/2013/10/22/wireless-electric-buses-developed-utah/

          • No way

            That is an battery powered bus with no hydraulic system. What’s your point?

            Why do you refer to electric and battery solutions and then randomly add “hydraulic hybrid”?

          • José DeSouza

            And I was simply referring to a more efficient means of collecting electricity other than inductive charging and as a means to avoid carrying onboard batteries. Did I make my point right this time?

          • No way

            I agree with most of your points, which are mainly about electricity and electricity transfers.

            I do not agree with you when you try to put in a hydraulic system into the mix. So just forget about that lousy hydralic system and we will be totally on the same page. :)

          • José DeSouza

            What′s so lousy about hydraulic systems? Electricity→stored mechanical energy→mechanical motive power versus electricity →chemical energy→ electricity→mechanical motive power? The fewer conversion steps you take the more efficient you are. That can be translated into more passenger.miles per unit of energy and economic input.

          • No way

            Yes, I agree. But only if you power it by electricity somehow. If you’re using an ICE with fossil fuels then any saves by being more efficient get’s wiped out and more so compared to running a BEV/PHEV bus on all electricity.

            But the hard part is not about choosing which regenerative braking system you should use for your trolleybus (no matter if it’s a battery, supercapacitor, hydraulic system, flywheel or whatever). The hard part is to sell and install the trolley system in a city.

            And then if you can’t get them to install it throughout the routes but only partially then we are back to a trolley bus combined with a battery to do the stretches without power. Hooking on and off the grid.

            A system that they have in the city of Landskrona

            http://www.slidein.se/en/about-the-project/

          • José DeSouza

            ‟The hard part is to sell and install the trolley system in a city.″.
            That′s precisely the point I′ve been trying to make all along.

            ‟…then we are back to a trolley bus combined with a battery to do the stretches without power‟.
            The ‟battery″, in that case, would be the hydraulic tanks themselves. You don′t need to carry both propulsion batteries and hydraulic cylinders onboard to store energy. Power is directly stored as mechanical energy rather than as chemical energy, which would be turned into electricity and finally back into mechanical power as in a BEV car. I′m an ardent fan of BEVs, believe me, but city buses, because of their frequent stop and go schedules, are a better suited for mechanical energy storage rather than chemical batteries. It′s a matter of efficiency that directly makes electric HHVs lighter, cheaper, more resilient and more economical to operate in the end. They can be ‛recharged′ at bus stops just like BE buses, as per the videos I posted above.

          • No way

            “‟The hard part is to sell and install the trolley system in a city.″”.
            “That′s precisely the point I′ve been trying to make all along.”

            If that’s the point you tried to make. Why haven’t you been writing about it from the beginning? The next time start with “I prefer a trolleybus over a BEV/PHEV bus and I want it to have a hydraulic system for regenerative braking.

            *sigh*… so we have a trolleybus with stretches without power. For the argument sake let’s say 3 km at the time. What is your plan for the propulsion then if you’re not having a battery and fossil fuels are off the table?

          • José DeSouza

            Hmmm, reminds me of someone who insists renewables aren′t feasible without lots of energy storage:
            http://img2.wikia.nocookie.net/__cb20120904213116/cartoonnetwork/images/0/05/DeeDee.jpg

          • Bob_Wallace

            Jose, what’s the reasonable distance one of these buses could drive on stored hydraulic energy alone? I’m assuming flat terrain for the moment and fully loaded with passengers.

            (Perhaps that’s already been said and I missed it in the comments and can’t find the info on the site you listed.)

          • José DeSouza

            It all depends on how much mechanical energy you have stored in your accumulator tanks. You can also design them for your specific needs. But the idea is simple: when you run out of ‟accumulated″ energy, you simply run your hydraulic recharging pump to top it up and there you go. That pump really doesn′t care whether it′s powered by an ICE or by an electric motor. If the latter is your option, then you arrange your charging stations along your route according to your needs. It shouldn′t be extremely difficult to figure out. In essence, your electric motor would work just as frequently as the ICE in the original concept. As to distances, relative conversion efficiencies and economics, no one has an answer yet. It seems I′m the first one proposing such an innovation out of existing possibilities.

          • No way

            So give us an example on how much energy you could store in an accumulator tank of a certain size and how far it would get a full bus.

          • Bob_Wallace

            Apparently we have three individuals, none of whom are mechanical engineers, in this discussion. Someone who works with hydraulic systems could probably pencil it out in a few seconds.

            Unless someone can come up reliable numbers what we’ve got is an interesting (at least to two of us) idea and little ability to take it further.

            The only numbers I’ve been able to find were some from 2012 which claimed a battery powered bus would cost more to own/operate than a typical diesel bus. Those numbers are now outdated with the BYD bus now cheaper. And a statement about carbon fiber accumulator tanks being expensive.

            Might be time to give this discussion a rest and hope that some usable data comes along.

          • José DeSouza

            Yes, I fully agree with you.

          • José DeSouza

            Similar to what is operating in Rome, Italy. No big deal.

  • Jouni Valkonen

    I would say that this bus could be cheaper to operate if ICE is replaced with overhead power lines. Of course this means that a city must invest on infrastructure, but generally if economy is in the slump due to lack of private sector investments, then it is not at all bad idea that public sector is investing on infrastructure. Infrastructure is typically better investment opportunity, because it returns long term returns mostly in form of welfare of people.

  • JamesWimberley

    What’s the price compared to the BYD K9? The tiny battery suggests that Volvo have made compromises to get a less alarming sticker price, though buyers will have to accept far less flexibility, and heavier investment in a dispersed charging network. It isn’t even the bus equivalent of the Toyota Prius with its 11-mile electric range.

    • Jouni Valkonen

      With small battery there might be also problem that to operate bus, daily cycles are too deep and therefore compromizes the longevity of battery. All electric approach is better because battery must be significantly larger than what is required for daily service, because bus need to be operational even then when the range is getting lower due to normal degradation of battery cells.

  • No way

    Boring… up to 75%? Why not make it 100% straight away?

    It has a battery for 7km on electricity from a 4,8 kWh battery. How hard would it have been to at least make it a Leaf size battery at 24 kWh? Or as big as the hybrid volvo cars of 12 kWh.

    It would make almost no cost difference but a great difference for the environment to get the last 30-50% too (up to 75% = maybe 50-70% real world).

    • Ronald Brakels

      It’s better than nothing and will teach the users they can save more money if they have all electrics.

      • No way

        It is better than nothing. But it would have been so easy to add batteries for maybe $3k more on something like a $200k bus (or whatever they may charge for it), still being a hybrid but a hybrid able to do full runs to the next fast charger on electricity. I’ve sent a mail to the project manager to maybe get a reason on why they did it this way.

        • Ronald Brakels

          When you look at the way the buses are used, with regular small charges at bus stops, it’s not so bad. But in a country where public transportation is seen as the enemy of people who pay politicians bribes, it’s not so effective as no one wants to pay to build the charging stations.

          • No way

            The bad part is that the bus is designed so that it can’t run on electricity all the way from one charger to another as the norm.

            And of course the bus company buing the buses will be building the chargers on their city routes so I don’t see any real problem there.

          • Ronald Brakels

            Looking at the price of diesel, getting enough chargers built for it to run off electricity basically all the time seems a no brainer.

            But getting chargers built in a place like where I live would be difficult. We are simply at a more primitive level of development than Sweden. The local council could build them but that would cost money and so that’s not likely to happen. And none of the private bus companies is likely to have the ability to invest in them either. No, we’re probably going to have to get long range electric buses that can be dropped in to replace the diesels as they wear out.

          • No way

            Any solution that get’s 100% electric (from renewable sources) is good. I know infrastructure is a hard sell in primitive societies but for city uses it would still be cheaper.

            You get one bus and two chargers for the price of one all electric BYD K9. And with more busses added you can add more chargers which serves more buses on different routes to a cheaper total price than having BYD K9’s.

            So looking at the over all economics this is a better solution.

            But in the end I only care about getting rid of the emissions, no matter if it’s Swedish, Chinese or US technology used.

      • José DeSouza

        Perhaps there′s something better than that better than nothing: http://www.altairbusolutions.com/

        • Ronald Brakels

          I think I prefer our Tindo all electric bus. It’s good, solid, New Zealand engineering. Now if only we had more than one.

    • Jouni Valkonen

      It is just surprising why any other manufacturer cannot replicate Tesla’s battery pack technology. Tesla has already solved all problems considering electric car batteries. They have high enough energy density and enough cycle life in order to offset the cost of battery cells.

      • No way

        Well, this has nothing to do with the battery pack technology. Even one of the worst packs of the EV makers today would easily fit and be cost effective in a hybrid bus. 4,8 to 12 kWh would still mean it’s half the size and price of a Leaf battery pack (assuming the same battery chemistry).

  • patb2009

    i hope this is extremely well tested and engineered.

    It would be bad if this were to become the next Grumman Flxible

    which we used to call the unFixAble.

    https://en.wikipedia.org/wiki/Flxible_Metro#_Litigation_resulting

    • No way

      That you don’t have to worry about. It’s made by some of the best engineers from one of the best companies with a strong focus on safety, reliability and efficiency.

    • Jouni Valkonen

      Volvo has done their work well. The problem might be is this done too well that it may not be cost competive relative e.g. BYD’s approach. BYD’s approach is getting year by year better as it is inevitable that the cost of batteries is getting down over time and the price of oil is volatile and unpredictable.

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