Electric / hybrid aircraft propulsion (NOT cars)

I really like how you keep seeing the big picture LeSving. Keep it up!

I think you are mostly right and the whole energy supply business will change a lot. In the long term we might even see national power grids being decommissioned in favour of local production and storage. Alternatively we need a European wide “smart grid” that would largely be able to even out the unsteady power generation by wind and solar plants.

One real upside of all this will be less reliance on middle eastern countries for fossel fuels. So hopefuly fewer wars and less tollerated corruption.

Peter wrote:

The PV panels don’t just last for ever

Peter dropped me a line on this topic. No one really knows how long they last. “Standard” solar cells made of crystalline silicon are a relatively recent invention from 1954, and there are plenty of stories about solar modules from the 50’s and 60’s that are still working.

The dominant cause of performance degradation is the EVA layer between the cell and the glass. This is a clear plastic sheet that is part of the overall laminate. The EVA tends to discolour with age, and therefore reduces the amount of light hitting the cell. A standard warranty will be along the lines of “80% nominal power output at 25 years”. As the technology improves along with the industry having more product history the terms of these warranties are creeping upwards.

achimha wrote:

We live in exciting times, my feeling is that most people underestimate the dramatic impact of what’s happening right now. It will come sooner and faster than we currently think.

Too right. I had eight very happy years in solar. The industry would constantly make growth predictions that seemed laughably bullish at the time and which then turned out to be underestimates! I’ve been out of the industry for two years now and it’s all moving so fast that I sometimes feel quite disconnected.

I have believed for a long time that the higher performance replacement for the smaller Lycoming won’t be a piston engine but will be an electric motor.

Not mentioned above….I think we may see Geothermal energy grow in importance as a major renewable energy source….probably eclipsing wind and solar in the future…

Peter wrote:

Currently we are at about 50:1 (battery weight versus liquid fuel weight, for same energy) so even allowing for efficiency gains you need to do a lot better than 5:1 to make it viable except for unusual applications (very short endurance, etc).

Currently we’re WAY better than 50:1. Effective energy density, taking into account efficiency:

Avgas: 11MJ/kg (ICE, 25% efficient)
Li-Ion: 0.78MJ/kg (brushless motor and controller, 90% efficient)

So currently about 14:1. Current developments (not yet commercially released) of lithium rechargable technology already double the energy density of Li-Ion.

Peter wrote:

I agree with the point about night-time grid utilisation, but this is applicable only once electric cars gets enough endurance to be chargeable primarily at night.

In other words already applicable for at least 10 years. A friend had a BEV (I don’t remember the model, but it was a French hatchback – normally a petrol model but this one was being sold as a BEV) ten years ago which had a 60mi/100km mile range. The average daily commute is only 15km (9 miles) and only about 5% of people have a round trip commute greater than 60km.

Range has gone up considerably since then. The smallest Nissan Leaf has a range of 124 miles/200 km. What fraction of 1% regularly drive more than 200km a day?

Peter wrote:

BTW a huge amount of energy was used to make those photovoltaic panels.

EROEI (Energy return on energy invested) for current solar panels is between 6:1 and 10:1. (Compared to Canadian tar sand oil production, which has an EROEI of only 3:1). EROEI of wind is about 18:1 (oil and gas today totals out about 15:1).

Would that be Lithium-Oxygen batteries? Or a different chemistry?
alioth wrote:

Current developments (not yet commercially released) of lithium rechargable technology already double the energy density of Li-Ion.

alioth wrote:

The smallest Nissan Leaf has a range of 124 miles/200 km. What fraction of 1% regularly drive more than 200km a day?

I think people don’t typically select a car based on what they normally do, they buy on what they need to do occasionally. That’s why most cars have four or six seats and are mostly driven solo. Also, risk management for anybody involves considering both the chance of it happening and the consequences of it happening. The consequences of running out of energy in a electric car are relatively high, which in my view means people tend to use no more than 2/3 of the available energy per day, or maybe half depending on their risk tolerance. BMW recognized this in supplying a small IC engine for ‘get home’ risk reduction in their electric car, but that increases complexity and maintenance cost.

One of my coworkers bought a new Tesla sedan recently but kept their old Lexus for those reasons. About the same time I instead sold my ‘driver’ and bought a new gasoline powered replacement. It cost $22K out the door (tax included) and does everything the Lexus plus the new $80K Tesla can do in combination. I drive a lot and the fuel cost is about 1% of my gross salary. The money saved goes into investments.