25
Oct

Phase 2 of project – Solar (PV) Electric “fueling” a.k.a. “free miles from the sun”

Written by admin. Posted in Build Diary, Build Diary, e-CarE46, e-MotoCRF250R, Solar

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With a modest solar array, approx. 11×33 feet, mounted on the south facing roof of the house, the net average cost to drive 40 miles daily is $0 annually, in fact, our founder driving the electric BMW325i , is currently achieving a net positive in power generation.  Not only is this electric BMW325i now higher performance in every way, it is also being fueled 100% by sunlight, truly Net-Zero on energy!  On the R&D lab/shop, a 5.6kW rooftop mounted and grid tied solar array delivers 17,000 miles worth of driving energy annually in the Portland Oregon area.  The solar array puts its power onto the grid during on-peak time, where the BMW’s battery pack is charged during off-peak time at almost half the cost. With solar and “Time-Of-Use” power billing, a profit is made in addition to the 17,000 miles of free driving that covers the cost of tire wear, which is the only real service the vehicle has after the conversion.  With a power inverter directly connecting the solar array to the electrical grid, the power meter spins backwards during daylight hours. When you come home, you just plug into the AC outlet and take back the power you generated during the day. This is very beneficial to the power grid by helping reduce the peak load during the day as a side benefit.  You can size the solar array to match the power used in your normal daily drive.

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Regarding the amortization of our EVDrive, Oregon shop PV array factored into the cost of driving the EVDrive BMW, we have accounted for it.   In our case, the system cost after state and federal incentives was $4300 out of pocket cost.   To get the $10,000 grant money from the Energy Trust of Oregon, we are required to meet at least 75% solar exposure.  Since we had tall trees reducing the exposure below 60%, we needed to remove enough to get up to around 80%.  The harvest resulted in 3 full log truck loads of straight fir log sections that returned $4600, prior to taxes.  So our out of pocket expenses are already paid for.

We are currently on track to put greater that 5MWhr onto the grid this year (with a few weeks of best solar of the year we are at 4.7MWhr now).   This results in over 17,000 miles of driving the EVDrive BMW per year, calculated by multiplying 3.5 (miles/kWhr) times kWhr (solar onto grid -which includes charging efficiency going into BMW pack.)

Now, to reconsider the emission profile with the solar array just mentioned above, there are no emissions. None. Not even battery cells venting. In fact, there will be little brake dust left behind with most of braking done with regen control now affixed near hand brake.

Regenerative (regen) braking. This drive system has the ability, and the battery system has the performance to capture over 80% of the braking energy, in this case from the rear wheels. The original brakes are still there but used less often as regen is used based on the opportunities when slowing. We will initially have an independent control for regen braking that will turn on the rear brake lights when the regen slider goes beyond a set point. This will allow some slowing that acts like “engine braking” without having brake lights come on. This makes driving down hills and city driving particularly efficient since the wind load is low and there is a lot of brake use required which returns more power back. A front wheel drive, or better yet a 4WD design would capture the majority of the kinetic energy back into these battery cells.

No engine noise. If you can’t imagine not having the rumble and revving of an internal combustion engine(ICE), think electronic amplifier driving a good sound system with whatever type engine sound you download; model T, ’69 small block Z28, ferrari etc. Silence is a now a choice. In town, around crosswalks, we are sure there will soon be a requirement that noise be generated for the less than 10 MPH speeds for pedestrian safety. Fine, that is a trivial detail.

There is only one moving part in the motor: the rotor spinning on bearings. The service and maintenance drops significantly. The most significant service needed: Tires. Those that look at the project pages will notice we are using a transmission with oil in it. Well, no service needed there either since the original BMW 5 speed transmission requires no oil changes in the transmission’s lifetime BMW says.  However, just to err on the safe side will change the 2 pints of fluid after 10 years.

Having this high performance actually improves the efficiency of the “grocery getting” driving. Here is the reason: When an electric power source is designed for and capable of delivering large currents with little loss, the losses become insignificant when lightly loaded.Unlike an internal combustion engine (ICE), the electric drive system doesn’t sacrifice mileage or efficiency for performance! Imagine having high performance AND ultimate economy combined!

The battery cells are non-toxic and completely recyclable after more than a decade of use, where90-95% of the Lithium is recovered. This means less to scrape from the plateaus of Bolivia. Typically, when cells are considered “depleted”, there is still 80% capacity left to serve a second life as energy storage cell banks for fast charging stations that can dump enormous currents for charging vehicles in 10 minutes (assuming high current cell type like we are using)

 

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