The Future of Transportation

"If I had asked what people wanted, they would have said faster horses." 

-Henry Ford

I've been wanting to write about this topic for quite some time, and given the recent buzz from Google and others, now seems to be a good time. The topic is self-driving, electric vehicle car-sharing, and I believe it has an amazing potential to change how we view personal transportation.

I've mentioned before in this blog the interplay between efficiency and economics of electric vehicles. Electric vehicles may be about $10K more expensive, but they are 1/6th the cost to operate. I had said that in the case of high gas price, EVs become much more economically attractive. They also become much more attractive if the mileage on them increases; the farther you drive, the more you leverage lower operating costs to your advantage. The problem is Americans don't drive enough. Well...I mean, Americans drive plenty, but not enough to currently offset the spread between our extremely cheap gasoline and electricity. In order to make the spread work more in our favor, we have to increase the number of miles traveled/vehicle; that means car sharing. Car sharing is a great idea. We are terrible at making good use of our own cars; we drive them just 30 miles/day on average, and we're in them only for an hour a day, leaving them sitting unused for the remaining 23 hours [1] (as an aside, the National Household Travel Survey from the US Department of Transportation is a pretty interesting report; you ought to take a look). Car sharing drives up vehicle utility.

To look at how electric vehicles could impact a traditional car sharing company, I looked up one of Zipcar's last shareholder annual reports before they were bought by Avis [2]. In addition to having to look up the difference between "revenue" and "income," I also had to look up some assumptions for cost of vehicle ownership [3], fleet mpg [4], gas prices [5], and some of Zipcar's historical data from Wikipedia [6]. Here's the breakdown from 2012:

• 770,000 members, 10,000 vehicles
• $280 million in revenue, $15 million in profit ($10 million from some "tax thing")
• From revenues:
• $40 million from membership fees
• $240 million from usage payments (I simply assumed the remaining revenue)
• From estimates on costs:
• $100 million for gas
• $24 million for vehicle acquisition in 2012
• $24 million for parking space costs
• $12 million for insurance
• $5 million for maintenance

It was here I realized I was $115 million short on costs. I also failed to remember Zipcar is a company that needs to do things like "pay employees" and "run marketing efforts," so I included those [7].

• Additional estimates for costs:
• $70 million for payroll
• $20 million for customer acquisition
• Sum total of costs: $255 million

Not bad for an estimate of an entire company's cost and revenue structure; we're less than 10% off. If we were to wave the vehicle electrification wand, it would primarily impact gas costs (the largest fraction of costs) and vehicle acquisition. To that end, gas costs would now become electricity costs at $23 million based on similar vehicle class efficiency figures (I used the Nissan Leaf) [8] and 2012 electricity prices [9]. Vehicle acquisition costs would increase to $36 million. In this scenario, revenues are still $280 million, but costs are now $190 million, raising profits from basically break even to $65 million; a healthy 23% profit margin.

That was a straight swap of EVs for gas cars in an existing car sharing company. What about invoking the self-driving component? Well, that one is a little tricky. The closest analogy is Uber, and it took some research to figure out how they actually operate, as well as a leaked 5-week snapshot to get an idea of finances [10]. Uber works as the marketplace for taxis and black car services; they actually don't own any vehicles themselves. As such, I don't have a feel for operating expenses like I did with Zipcar. All I know is that from the fare the customer pays, Uber (primarily a software and marketing company) takes 20%, leaving the 80% and the rest of the vehicle ownership, maintenance, insurance, payroll, etc. to the taxi or black car company. Rather disappointingly opaque, but most Silicon Valley startups are like this.

Let's consider hypothetically starting our own company using shared self-driving EVs. In honor of rolling out fleets of Google self-driving cars, let's call it "Gaggle" (a terrible name; no one ever use this name). Gaggle's usage statistics are similar to Zipcar's: there are 77 members/vehicle, 6hrs of use/day on each vehicle, 180 miles driven/day in each vehicle. If we use the NHTS data, this means there are 6 trips in each vehicle/day. For simplicity, Gaggle charges on a "per trip" basis; think of it like a flat fee, or like a bus pass. Let's consider 2 scenarios corresponding to 2 prices: a $12/trip scenario and a $6/trip scenario. And let's do a simple payback period analysis where trip revenue pays for the initial purchase of the car. Consider a $20,000 base car, $10,000 for self-driving capabilities [11], and $10,000 for a battery pack. At $12/trip, the gas and electric self-driving vehicles don't look that much different. Gaggle's electric self-driving vehicle pays for itself in 1.6 years and racks up 109,000 on the odometer, while the gas self-driving vehicle pays for itself in 1.8 years and hits 117,000 miles. The $12/trip cost is roughly half that of Uber and about equal to Zipcar's economics. What about the $6/trip case? The electric vehicle pays for itself in a longer time, 3.6 years and climbs up to 240,000 miles: high but given EVs lower maintenance requirements, definitely achievable (would be about 2500 battery charge/discharge cycles). The gas vehicle on the other hand requires 8.2 years and needs 540,000 miles to pay it back; this is definitely a vehicle replacement, further impacting economics.

Due to the lower operating cost of self-driving electric vehicles, Gaggle can offer cheap, convenient private transportation that makes a strong business case for profitability. Gaggle can reduce traffic, reduce pollution, and reduce frustration, all for about the cost of grabbing lunch out. Car sharing has never been better.

World: meet Gaggle.

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[1] http://nhts.ornl.gov/2009/pub/stt.pdf
[2] http://www.zipcar.com/press/releases/zipcar-reports-fourth-quarter-and-full-2012-results
[3] http://org.elon.edu/sustainability/documents/Zipcar%20FAQs.pdf
[4] http://www.nhtsa.gov/staticfiles/rulemaking/pdf/cafe/April_2013_Summary_Report.pdf
[5] http://www.eia.gov/dnav/pet/pet_pri_gnd_dcus_nus_a.htm
[6] http://en.wikipedia.org/wiki/Zipcar
[7] http://www.marketingsherpa.com/data/members/handbooks/2012-Lead-Generation-Benchmark-Report-EXCERPT-5-23-12.pdf
[8] http://www.fueleconomy.gov/feg/Find.do?action=sbs&id=30979
[9] http://www.eia.gov/electricity/monthly/pdf/chap5.pdf
[10] http://valleywag.gawker.com/matt-durham-an-analyst-at-an-ecommerce-company-crunche-1476549437
[11] http://www.fastcompany.com/3025722/will-you-ever-be-able-to-afford-a-self-driving-car

Mars Climate Orbiter and Energy Models

Last post on this, I swear...

Due to a metric-standard measure conversion issue, I had accidentally reported the demand for EnergyStar clothes washers in L/cycle, not gal/cycle, leading to a much greater water demand than expected. History has a few cases where this doesn't work out so well: famously NASA's Mars Climate Orbiter which burned up in Mars' atmosphere, and an Air Canada flight that ran out of fuel halfway through its trip (the captain happened to be an accomplished glider pilot and successfully landed the plane). In my model, it significantly reduced the required water load. As such, there's a good 30% margin between water demand and supply. Here's the model if you want to take a look for yourself. For those of you reticent to download some stranger's Excel model, I've provided a summary:

• Cabin size (ft2): 545
• Cabin footprint (ft2): 375
• Occupancy: 2 continuously, 4-6 for weekend
• Rough cost ($300/ft2 + infrastructure costs): $210,000
• Solar PV demand (kWh/day): 11
• Solar thermal demand (kWh/day): 11
• Max solar insolation available (kWh/day): 2000 (excluding conversion losses)
• Weekly water demand (gal/week): 68
• Min weekly rainwater availabile (gal/week): 99

I've run out of things to be concerned about. I originally thought water would be an issue; apparently two people can live comfortably continuously on a 15'x25' water collection footprint, and 4-6 can for a weekend. There's ample power to run the various infrastructure systems. And there seems to be enough space. I'll add that blackwater (i.e. sewage) processing seems to be an open question. Septic systems and aerobic digestion systems still require periodic sludge removal and composting toilets aren't all that familiar or easy to use (I did this research while having dinner last night: not the best idea). I now understand why the Bill and Melinda Gates Foundation is funding 15 teams to reinvent the flush toilet; waste treatment still is a hard problem to solve.

Bottom line is living comfortably off of naturally locally available resources isn't nearly as hard as I had originally expected. With some good engineering and clever design, a very comfortable, modern, sustainable living can be made.

Zero-Energy Cabin: Update

"I went to the woods because I wished to live deliberately, to front only the essential facts of life, and see if I could not learn what it had to teach..."  - Henry David Thoreau, Walden

Last night I had released the output of my model for a zero-energy, off-grid cabin designed for upstate VT. I've been thinking a little more about it and have made some updates. I've also torn a page from Thoreau and decided some conclusions drawn from the exercise might be worth going over.

1) I haven't given adequate consideration to ventilation. Without good ventilation, issues from general stuffiness to mold can occur: not good things. Running the numbers I was surprised how much it mattered. I used some of the passive house standards, which rely on air-to-air heat exchangers to reduce heating loads. To comply with 0.6 air exchanges/hr with an 80% eff HX, I need to add 5.5 kWh/day to my heating load (10x my previously calculated heat loss). I also need to change the layout of my floors. Previously the only floor-to-floor ventilation was through a small 3'x2.5' ladder opening. I've set back the 2nd floor and apex floor to also permit a 6'x3' opening from ground floor to roof. Such an arrangement allows for better floor-to-floor ventilation and, if the top windows can open, a passive cooling structure powered by the morning sun as well.

Set-back 2nd and apex floors for ventilation, plus proper orientation.

2) I've also updated my water usage requirements. Turns out my first consumption estimate was too high. This might be filed under TMI, but it can't be as bad as other "living as nature intended" blogs I've read or come across. My shower estimate assumed 10min of water use at 2gal/min. I timed myself this morning before work just to see. I take "naval showers" (water on -> wet up -> water off -> lather up -> water on -> rinse off -> water off) not for environmental considerations, but out of preference; I'm not a small guy and my shower stall reminds me of that on a daily basis. That said, having timed my morning shower, it's a comfortable 5 min of "water on" time, thus cutting my consumption in half. I've updated my water consumption model to reflect that, and found that I could squeeze 4 naval showers with a low-flow shower head (4x10gal), 1 load of dishes in an EnergyStar dishwasher  (4 gal), and 1 load of laundry in an EnergyStar washing machine (40 gal!!!) per week. This is perfectly sufficient for 4 people for the weekend or 2 people living continuously. I was actually a bit surprised by this, as water use seemed to have been the hardest constraint to satisfy.

3) Now for some general lessons:

- The biggest drivers were heating: incoming air for ventilation and hot water for cleaning. I find that pretty remarkable. With respect to heating air, the amount of energy is dependent on number of air-exchanges/hr, which is entirely determined by the volume of your house; heat loss through insulation can be made marginal, but air-exchanges are a big sink. Smaller house -> lower energy consumption. Period. With respect to heating water, it's all about consumption; using less water means having to heat less water. A real win-win. We really should do what we can to cut back on hot water consumption.

- As I mentioned before, the hardest challenge was water consumption. I really think this is telling as I believe that our future will be water constrained more than power constrained. In this example, if I needed more power, I had plenty of room for more solar panels; it would just cost a little more. If I needed more water, I was in trouble. Water conservation is a serious thing. I'll discuss more about it in another post.

- All in all, the exercise wasn't that hard; in a day I managed to put together a design for a small cabin with rainwater collection, greywater recycling, solar thermal heating, and PV-sourced electricity that featured all the comforts of modern living: heat, hot water, internal plumbing, TV, ventilation, oven, refrigerator, dishwasher, washer and dryer. This cabin could comfortably house 4-6 people over the weekend (giving time to bank water and power resources through the week), or 2 people continuously. By my estimates, it costs about $200K: same as the median house price in the US. In short, it's a pretty serviceable home, implying I don't think that zero-energy homes are some future fantasy, but a realizable present option should people want to pursue them.

I really liked this exercise. I'm surprised-but-kinda-not that I was able to design a comfortable home that was completely off-grid. I'll see what I can do to upload the model for review.

I Got Bored So I Designed an Off-Grid Cabin...

It's always been a dream of mine to have a cabin in the woods as Henry David Thoreau did...though perhaps more of a comfortable ski cabin in VT than a small shack on a lake in MA...so I guess not as much as Thoreau as I'd like to let on. Either way, the thought stuck with me so unrelentingly today I had to put it all down on paper.

First, let's identify our constraints. In building his cabin, Thoreau scavenged for his building materials. I'm looking for something a bit nicer, so the option is to either build it on-site (difficult to do in remote locations), or build it pre-fab and ship it. Being more a fan of the latter, you can't just slap on any size house on a truck; they're usually pre-fab modules less than 15' wide and 30' long. So let's choose a footprint 15'w and 25'l. Second, let's assume we're remote enough such that we don't have access to power, water, or sewer connections.This is where things get interesting... In designing zero energy homes, two goals must be simultaneously achieved: maximize power production and minimize energy consumption. Maximizing energy production in our remote area will be achieved by solar energy (PV and flat plate thermal), and minimal energy consumption is done chiefly through heavy insulation and good resource (namely water) management. Since we're relying on the environment for our water and power, we have to take into consideration our area's solar insolation and average rainfall. I've chosen upper VT with data from the new US Climate Data website and NREL [1] [2]. Finally, some aesthetic considerations. I've always liked A-frame houses; I think they're well designed for low-energy homes in wintry climates, so let's use that as our model.

My model outputs a 575 sq. ft. cabin with room for 3 queen beds and 1.5 bathrooms, a large 10x7 kitchen, and plenty of space space in the wings for infrastructure. Using some estimates from David MacKay's amazing book Sustainable Energy without the Hot Air, I've estimated a 10kWh/day electricity usage and 14kWh/day thermal usage (almost all of which is in warming up water). To satisfy that demand, 33m2 of 10% solar panels in VT's 3 kWh/day/m2 solar flux would do it, same with 7m2 of 65% efficient flat plate water heaters for the thermal load. Those areas may sound like a lot, and they are, but another reason for my choosing an A-frame house is the very large roof area to work with.

Roughed out section and floor plan. Things are about to scale.

Because of the large roof space, power isn't a problem; we're taking up just over 60% of the south-facing roof. The high-sloped roofs and small footprint do resort in another problem though: water availability. Remember, I'm leaning on rainwater collection instead of a city water connection. I've calculated that only about 90 gal/week of water is available during the dry winter months due to lack of rain fall, rising to just over 225 gal/week in the summer. 90 gal/week is nothing; it would be the equivalent of 4x10min showers with a regular high-volume shower head. It certainly isn't much beyond a weekend cabin during the winter. I'm trying to stretch that out with low-flow shower heads, a recycled greywater system for flushing toilets using sink/shower/dishwasher effluent, and large cisterns to hold about a month's supply of water. 

My best guess as to what a low water-intensity plumbing system would look like. It should be noted, I am not a plumber...

I did learn a couple of things, especially about plumbing. I originally thought water pressure was going to be a huge problem, and started to work on a fancy gravity-based system, but I learned that there exists simple automatic pumps that turn on and deliver 40+psi pressure when they sense an open valve down the line. I also learned that while rainwater can be held for a while, greywater must be disposed of no later than 72 hours or else the organic content in it turns foul. You can also apparently run a septic system in freezing climates, provided you just dig down far enough below frozen ground (+18"), hence my choice of septic system vs. composting toilets.

So there it is, a zero-energy, off-grid weekend ski cabin with all the comforts of home. Based on upper bounds of modular home estimates, I've pegged the cost of this cabin to be $200K with all the PV and energy storage costs included (I think Thoreau said he paid $28 in 1845 for his). One day I hope to actually build this. Maybe I'll write about it then...

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[1] http://www.usclimatedata.com/climate/vermont/united-states/3215
[2] http://rredc.nrel.gov/solar/pubs/redbook/PDFs/VT.PDF
[3] http://www.withouthotair.com/Contents.html