What ever happened to HHV technology?
 

Back in 2008, the United Parcel Service (UPS) decided to deploy a few hydraulic hybrids for their delivery fleet.

https://s29755.pcdn.co/wp-content/up...hybrid_UPS.jpg

A few cities also bought several HHV garbage trucks. Then there started to be a small trickle of news claiming that hydraulic hybrids could have a future in everything from very large commercial vehicles to passenger vehicles to bicycles.

http://www.youtube.com/watch?v=o_19jOV8UW0&t=32s

A few companies even started offering HHV conversions for existing vehicles. But a quick search on google seems to indicate that they've all stopped offering such services. The idea seems to have fizzled with no new news on further developments.

But what happened to HHV technology?

The technology looked very promising, and still does to an extent.
With regenerative braking efficiencies claims of up to 80% and potentially double the fuel savings, hydraulic hybrid technology had been lauded as being even more efficient than electric hybrid technology and potentially cheaper. The concept was proven to work even in very large commercial vehicles.

http://www.youtube.com/watch?v=H-FlXKNg8Ls

But none of that has seemed to help HHV news from disappearing. What happened to the HHV?

Was it that it was too expensive to make? I noticed that Orlando's HHV garbage trucks cost them over $150,000 more a piece, or about 165% what a non-hybrid truck would have cost.

Was it that other technologies eclipsed the interest in them? If you look at Orlando's latest purchases in trash trucks they've now switched to apparently non-hybrid CNG trucks.

EV's also may have caused a loss of interest in HHV's kind of the same way EV's have caused some to lose interest in plug-in hybrids.

Is there some other reason? Did they not get the efficiency that they were expected to get? Did they have reliability problems? Or is this a highly efficient fuel saving technology with untapped potential that everyone has aparently forgotten about?

http://www.youtube.com/watch?v=FpthKavtSSo

I guess I may have at least partially answered my own question. Lightning hybrids was one of the companies that was developing and selling hydraulic hybrid conversions. They are now focused on EV's.

https://companyweek.com/article/lightning-systems

I would venture to guess the development/production/manufacturing costs simply don't provide enough of a benefit over electric hybrid or EV.

It's always been about the best way to store energy. They are all fighting a tough fight as gasoline stores so much energy per kilogram and "recharges" in seconds.

When these were being developed did they have Li-ion batteries yet? There were also flywheel busses in development as well. They would respin the flywheel every so many stops.

Batteries became cheap.

Very probable.

The hydraulic hybrid was never intended to be a means to store massive amounts of energy but to work exclusively as a traditional hybrid that helps save fuel through regenerative braking. It only makes (made) sense on stop and go vehicles. Vehicles that cruise down a highway wouldn't benefit much from the regenerative braking.

At the time there weren't any Li-ion hybrids or EV's. The only thing that came close were the NiMH hybrids, namely the 1st Gen Honda Insight and the 1st and 2nd gen Toyota Prius. The NiMH hybrids were said to get up to 20% or 25% regen efficiency and weighed more per unit of power.

By comparison, the hydraulic hybrid systems that had been developed and tested at that time were 70% to 80% efficient at regenerative braking and were light enough to be easily adapted to commercial vehicles that normally need all the weight savings they can get in order to haul their cargo. For an example, on a full sized bus the hydraulic hybrid system might mean you would lose one passenger in capacity. (This is why many have serious doubts about a Tesla or other company produced battery electric semi truck. The added weight of the batteries displaces the weight of the cargo that can be carried.)

Anywho, for hybrids at least maybe the lithium ion battery caught up to and surpassed the hydraulic accumulator in power to weight ratio or effiency (I've seen claims of Tesla regen being 85% or even 95% efficent although I have serioius doubts.) Even if li-ion batteries don't surpass it in those aspects, they definitely do in terms of energy density, making li-ion batteries better for certain applications.

For an example, anything plug-in (hybrid or pure EV) would benefit from a li-ion battery. Also when traveling over mountains a lithium EV or hybrid system would help soak up energy while regening down the pass. These are things that cannot be done in a hydraulic hybrid.

I think what attracts me to the hydraulic hybrid idea is that it isn't affected as much by cold weather. My NiMH hybrids suffer quite a bit during the winter, and I'm sure a lot has to do with battery temperature since I can warm up the engine and catalytic converter, keeping the heater off, and still drive around without the engine ever wanting to shut off. And in our Nissan Leaf the cold still took a huge toll on range even when trying to hypermile without turning on the heater.

Hydraulic hybrid setups are quite mechanically complex compared to Toyota's HSD and other similar hybrid electrics, or even some serial hybrid electrics such as the Wrightspeed Route system.

What happened?
Batteries.

Does that mean there are a lot of electric hybrid or full BEV delivery trucks, trash trucks, metro buses and school buses now?

Or why did places like Orlando change their hybrid trash trucks in for CNG non-hybrid trucks?

It appears to be the solution no one wanted.
It hydraulic hybrids seem to work great and nothing is wrong with the technology.
But the prices of hydraulic gear appears to be increasing while batteries and inverter tech keeps getting cheaper.