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Cold weather doesn’t make for a happy Volt

One external factor that’s hurting the number of miles we can run on a full battery charge is the winter. Under typical driving and climate conditions, GM says the 2013 Volt should get around 38 miles of travel on a single charge. But like any batteries, those in the Volt are adversely affected by cold temperatures. As a result, we’ve experienced some driving days where we only get 34 or 35 miles on car’s battery and then the gas generator kicks in.

The engine has also turned on sporadically to maintain the battery temperature; even when there’s still plenty of juice in the power pack. I’ve noticed this when the temps drop below 35-degrees or so, which is common right now where we live in Pennsylvania. These few periods when the engine heats things up a bit don’t use up much gas however. The engine might run for two or three minutes at a time.

We’re using more electricity, but still not paying for it

Part of the reason we decided to get a car that runs primarily off of electricity is because we’re creating more electricity than we use on an annual basis. In the last 12 months, our 41 solar panels produced 13.8 MWh of electricity but we only used 7.5 MWh of it. Of course, recharging the Volt’s battery on a daily basis is increasing our electricity consumption. It takes roughly 10.8 kWh to fully charge the Volt, which costs us about $1.18 and takes 10 hours with the standard charger.

Although the month of December isn’t over, I checked our electricity usage to date and found it to be 628 kWh so far this month. A quick peek at our home’s solar energy electricity production show that we’ve only produced 462 kWh of energy, so we’re at a deficit. (Note: Our solar array data is made public in real-time here.) I’m not concerned, however.

We’ve built up enough of a surplus with our energy provider so we’ll simply tap into that reserve instead of paying a bill this month. And the winter months are known for both their shorter days and a lower sun angle, so I’m not surprised that we haven’t created enough electricity to have a surplus. That’s sure to change as the days get longer: Last June our panels produced 1.48 MWh of electricity, or nearly four times that of the current month.

Even though there aren’t too many public charging stations in our area, I have found one at the King of Prussia mall, which is the second largest mall in the country and local to us. Atop one of the parking garages are two spots dedicated to electric vehicles, complete with a pair of 240V charging stations. There’s no cost and we’ve taken advantage of them three times already. By the time we’re done shopping, our Volt battery is fully charged for the ride home.

Savings are looking good

Even though we’re tapping our personal reserve of electricity, we’ve come out way ahead in this first month. It was a typical driving month for us, in terms of mileage, but didn’t really cost us anything out of pocket for fuel. The prior month, we drove roughly the same miles and spent just over $227 in gasoline costs.

This month we didn’t see an exact savings of that figure, of course, however the first tank of gas in our Volt was provided by the dealer. And, as noted, we won’t pay anything more for the electricity used to charge the Volt. If we can fill up the tank once per month — at a cost of around $35 for the small tank — and produce enough electricity from the sun, we will have drastically cut our costs for fuel.

Fun to drive at the same time

Not only are we saving money, but we’re having fun driving the car. I really enjoy it. It’s almost like a game to me: Getting each ride to be as efficient as possible. We haven’t really been limited by the fact that only four people fit in a Volt but it could be a future inconvenience. We have two kids, so in most cases, we’re fine. If the kids have a friend over and we have to go somewhere, either  my wife or I ends up staying at home. If nothing else, it gives one of us an excuse not to be the kids’ chauffeur.

I still haven’t enabled the OnStar account, so I haven’t yet been able to play with the smartphone apps. I’ll do that over the holidays. I’ve also ended up saving myself $10 a month by cancelling my Rdio music subscription and just using Pandora in the car over Bluetooth. There’s a dedicated Pandora app that displays album art and supports the thumbs up / thumbs down rating activity on the car’s touchscreen.

So far there isn’t much that I don’t like in the Volt, save perhaps the many touch buttons in it. All of them are labeled against a white background — at least in our model — and can sometimes be hard to read. Without a doubt, you really have to look the console to find the right button, which can be a safety issue. My way around that has been to make very good use of the car’s integrated speech recognition system, which works quite well for audio and climate controls.

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Using MeterPlug looks pretty simple: Just plug it in to an outlet and connect any appliance you want to monitor into the Meter Plug. You’ll see actual energy usage for the appliance on an iPhone or Android handset that supports the Bluetooth 4.0 LE standard. The MeterPlug itself uses a scant 0.1 watts of juice, so using it won’t add any noticeable cost to your utility bill. And when the MeterPlug sees that a connected appliance hasn’t been used for a while, it cuts the power to eliminate any “Vampire” drain.

On the phone, you can turn on or off a device connected to the MeterPlug, which is a nice extra, but the real value is in the energy monitoring. With the companion app, you can view consumption history over time or the actual current use and cost, based on electricity prices. Armed with that data, you can see which appliances are using more electricity than others, which could help you decide when to upgrade to a more efficient model.

I like the idea behind the MeterPlug, but it may be a little expensive for most. Currently an IndiGoGo project looking for funding, it will cost you $45 for one. That’s a discount over the expected $60 retail price, but to get the biggest benefit from an energy monitoring approach, you’d really need multiple MeterPlugs. If these were to some in around $25 to $30 each (or less), I could see a much bigger audience.

The team behind MeterPlug will be demonstrating the gadget at next month’s Consumer Electronics Show, so I plan to take a closer look at it. We already monitor our power, mainly because of our 41 solar panels generating electricity, and have smart strips that kill of vampire drain when appliances aren’t in use. I think we’re in the minority however, so I’ll dig for more info on the Meter Plug at CES.

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Most of the sectors that GE’s newly coined effort covers — transportation, aviation, locomotives, power generation, power distribution, oil and gas development, and industrial processes — are highly energy-reliant (if not all about energy) and the use of digital technologies in these sectors is meant to enable the use of energy (electricity and fuel) as efficiently as possible. That’s where a lot of the cost savings lie. The one exception in the mix is GE’s attention on digital health care.

GE says that with digital and sensor technologies, the commercial aviation industry could reduce fuel use by one percent, which is a savings of $30 billion over 15 years. A one percent efficiency gain for gas-fired power plants globally could deliver $66 billion in fuel savings. A one percent gain in efficiency for the world’s rail networks could lead to $27 billion in fuel savings. The list goes on — and it’s filled with energy efficiency measures, which equals cost savings.

GE has been classifying a lot of this technology under its Ecomagination brand, and it’ll probably continue to do so well into the future. Saving energy — electricity use and fuel — is clearly in the best interest of the planet. Burning fossil fuels for transportation and electricity is a major cause of climate change.

But GE’s CEO Jeff Immelt has said before that he regrets spending so much time over the past four years focused on how green GE’s technologies are. In the Spring of 2011, Immelt said at an event at MIT (reported by Reuters):

“If I had one thing to do over again I would not have talked so much about green. . . Even though I believe in global warming and I believe in the science … it just took on a connotation that was too elitist; it was too precious and it let opponents think that if you had a green initiative, you didn’t care about jobs. I’m a businessman. That’s all I care about, is jobs.”

The re-branding of green technologies — and the clean tech sector — is happening across the board. The term cleantech (and green for that matter) have been deeply politicized in the U.S., and have become a dirty word in some post-Solyndra circles. From a startup perspective, venture capitalists and entrepreneurs have had a harder time making money in “cleantech” than in mobile and web ventures.

As a result some investors — and some innovators — have moved away from so-called cleantech. The term “smart grid,” too, has been a bit tainted as consumers have pushed back on smart meters in certain regions. Smart grid returns for investors and startups have also been scarce. Investor groups looking to rebrand cleantech have been emphasizing terms like Clean Web, digital green and the intersection of cleantech and IT.

But as I reported recently, the trends behind the cleantech movement (and the smart grid) are still in place: there will be 9 billion people by 2050, which will lead to resource constraints, and a need for the better management of resources (energy being a major one). GE seems to be at the forefront of trying to rebrand this trend with this Industrial Internet moniker — and I applaud that.

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First things first: Decisions and costs

Our family has always tried to be green when possible. We’re avid recyclers, we tried a small composting project, we use CFL or LED bulbs throughout the house, and I can’t tell you how many solar-powered chargers I’ve tried for my mobile devices. (The most recent one is outstanding.) But we never had the money to “go solar” even though we wanted to. That changed due to a unique financial situation. In the spirit of transparency, I’m going to share the details.

My wife inherited a family member’s IRA account several years ago and the law required that the funds be liquidated over a five-year period. We got to the final year in 2011 and realized we were going to be hit with a large tax bill on the remaining IRA funds and decided to invest the funds into something with a tax incentive. After much research on solar energy — this is a great site to estimate system sizing, pricing and benefits – return on investment and such, we decided to go with solar panels, moved in part because our rear roof faces south.

It turns out that a local contractor nearby put solar panels on his office and became a certified solar panel installer. I requested a number of quotes from companies in the area, but he gave the best price at the time: $5.50 per watt. I then looked at our electricity usage for the prior year — we’re a family of four, with two full-time work-at-home people — and over-specified the system by 25 percent capacity for two reasons. We have a four bedroom house, so I planned for the next homeowner to have five occupants. And I wanted to maximize the tax benefit, which was a 30 percent federal tax credit on the entire project.

The specified 9.43 kW (DC) system turned out to be 41 panels — 230 Watts each — which produced 12.05 megawatt hours of electricity from Nov. 1, 2011 to Oct. 31, 2012. That cost us $51,865 up front, including installation, permits, inspections, parts, labor and warranty. Yup, it’s a big chunk of change but that federal tax credit totaled $15,560, which helped offset taxes on the IRA liquidation. And many states offer rebates on solar projects; ours provided us a check for around $7,100 once the system was up and running. Our net cost then was $29,205.

It’s also worth considering companies in some states offer no-money down solar panel systems: essentially you let them install a system on your property and then lease the system. The company itself reaps the incentive benefits, but you may save money on your electricity bill.

Installation of the puzzle pieces

I had thought the system would be complicated by many parts, but it’s actually quite simple. Obviously, we have the panels, which generate electricity from sunlight. All of that power is DC, or direct current, so the system needs an inverter for AC power. We considered one single inverter but instead opted for individual microinverters attached to every panel. There are several benefits to this approach.

For starters, if one panel or inverter fails, it’s easier to locate and fix the issue. Second, the microinverters feed real-time data from every panel via Ethernet over powerline  to a small web server included for monitoring purposes. I can get tons of useful information from the system. You can view most of my system details here online, for example.

The microinverters, as well as the small web server that tracks them, are made by Enphase. Each one converts the DC power from its connected panel to AC power. Each microinverter is linked to the next one in the solar panel array so essentially, these are plug-and-play devices. Each connects to the next, and the last microinverter feeds a power line, which we fed through our attic and down along the outside of our house near our electrical meter. The panels themselves are attached to the roof with aluminum framing so the install process is fairly simple: Install the frame, connect the microinverters to their respective panels, attach the panels to the frame and link the microinverters.

Because of the solar panels, two additional electrical meters were needed. We still have the original meter that measures our electricity use from the grid but a new meter is needed to measure power output and a third measures the difference between electricity created and used. More on that in bit.

So how well is the system working?

In a word: great! In this graph below — from Enlighten’s web service that creates reports from our solar panel system — you can see exactly how much energy we produced on a daily basis.

In fact, this graph gives you rough history of the weather where we live in southeastern Pennsylvania. The drops on the graph represent days with little or sun, although even on a cloudy day we make a little energy. You can also see when the days get longer and provide more direct sunlight to our roof; we’re in the downward trend now as the shortest day of the year is approaching. Here’s a look at the numbers for production and usage by month:

There’s no maintenance to the system; it’s just always working to create power when there’s enough light. I haven’t yet had to do a thing to the panels, which have a 25 year warranty, same as the microinverters. So with the solar panels then, you’d think we’d be fine during a power outage, like the one we experienced for 4 days last week. Not quite….

Different systems for different needs

One of the upfront decisions you’ll need to make when planning a solar panel system is will you still be tied to the electric grid? Or will you go off-grid? There are pros and cons to each; the former costs less up front while the latter provides stored power during the evening hours or during an outage. Since we had no power during Hurricane Sandy, you can guess which system we have: One that keeps us tied to the grid.

That means all of the power our panels create is actually fed back into the grid; we still get all of our power from our electric company in this configuration. And in the case of an outage, grid-tie systems such as ours are automatically disabled. Why? Because if we were feeding power into the grid during an outage, it would be unsafe for the workers trying to fix the outage.

To go completely off-grid and have batteries store excess power would have added approximately 20 percent to our up-front project costs. My wife felt we’d never regain that cost because we rarely have outages. During Hurricane Sandy, of course, I gave her one — and only one — light-hearted “I told you so.” And at this point, I’m reconsidering what to do for backup power, but that’s another post for another time.

Is solar right for you?

I can’t answer that question, but hopefully, I’ve provided some insights to help you decide. Having a house some south-facing roof is a must unless you plan to have panels on your grounds. Local or state incentives vary by location as well so you’ll need to check them in your area.

The biggest issue for most is likely the large up-front cost involved although you could start small and build up the system over time. I can’t argue that the costs are still high, although they should be lower now than a year ago. And the payback period — which will vary based on your system, location and energy costs without solar — can be high. Our break-even point is around 7.3 years, but that includes the home appreciation expected due to the system.

We may not be here long enough to break even but we’ve already gained an appreciation benefit from the panels. Taking advantage of the low rates, we refinanced our home last month and the added value of the solar panels was around $30,000. And why not when the next owner of this home is unlikely to have an electric bill ever? We were paying around $2,500 per year for electricity before the system was built; now build up a credit in most months. But for us, it’s not all about the money or the investment, even though we have a hedge against a rise in electricity costs: Any price increase means we’ll get more for our excess energy production.

We feel we smartly took advantage of certain tax incentives, added value to our home and are one step closer to being energy independent, save for a backup system. If I could go back in time, I’d probably add some type of battery backup. At this point, we’re making enough excess power that we’re considering a plug-in car to replace our current vehicle. Why not let the sun power our home and our wheels while cutting down on our annual gasoline costs at the same time?

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Another domain in which energy and water concerns collide is in desalination operations. One possible solution to Southern California’s reliance on water pumped over mountains from the north is to make use of the ocean of water breaking onto the local beaches.

A recent blurb in the New York Times announced plans for a desalination facility just north of San Diego that would produce 50 million gallons of water per day — aiming to supply 7 percent of regional demand by 2020. The price tag is roughly a billion dollars. The conversion factor is thus about $20 for every gallon-per-day of capacity (at large-scale; likely fails at the household level).

The estimated cost comes to about $4.80 per hcf, which is higher than the current price of water to the end-user in San Diego. But I’m not knocking it on these grounds: many of our future options will likely be more expensive than the magic carpet ride we’ve enjoyed on the foundation of fossil fuels.

How desalination works

Energetically, the most straightforward approach to desalination is evaporating water and collecting the condensed vapor. Put salt water (or anything moist) in a dark container with clear plastic or glass across the top and place it in the sun. The interior will heat up and evaporate water, which then condenses on the cooler plastic/glass cover. An appropriate sloped-roof geometry allows drip-collection of the water.

A water desalination plant in Brazil

Every gram (mL) of water vapor that escapes its liquid birthplace exacts a toll of 2257 J. This is a bit steep. Heating that same parent gram of water by 1°C only costs 4.18 J — which is why a pot of boiling water takes ages to boil away to nothing (see post on boiling water efficiency). A brute force approach like this would demand 2.4 kWh of thermal energy for every gallon of water produced (or 633 kWh/m³)!

Until I did the math, I dreamed of flowing ocean water through a system of shallow, covered trenches, generating fresh evaporated condensate. Low-tech, solar-driven, lovely! We might optimistically capture 50 percent of the incoming solar energy in the trough-collector, so that each square meter receiving about 5 kWh/day of incident energy could result in one gallon of water. Producing 10 percent of California’s demand would then require an area 60 km on a side, or a strip of land along California’s entire coastline about 2.5 km wide. Let’s call that infeasible. Darn.

But there are back doors. For one, waste heat from power plants (including nuclear) can be used as the source of energy in a form of co-generation. Also, water can be made to boil vigorously at room temperature in a mostly evacuated system once the pressure drops to about one-fortieth of an atmosphere (~20 Torr). In this scheme, it would take about 34 kWh to pump out 1,000 L (1 m³) of water molecules against this pressure differential: a bargain compared to the 633 kWh/m³ from direct heating.

A GE water desalination plant in Brazil

Most desalination plants use the multi-stage flash distillation process, which employs low-pressure chambers and recovers much of the heat of vaporization as the vapor condenses on the feedwater intake pipes, reducing the amount of direct heating required. These devices tend to achieve about 18–25 kWh/m³, which, again, is a bargain compared to direct heating.

Finally, reverse osmosis (RO) is another option, forcing water through membranes that exclude the saline ions. Typical RO installations achieve about 5–7 kWh/m³ (see, for instance, here or here). But the osmosis approach requires high-grade electricity, which if produced in the traditional manner requires about 17 kWh of thermal energy input per cubic meter of water produced. So really these prevalent techniques are not tremendously different energetically, although perhaps the osmosis approach is more finicky in terms of water preparation/filtering, gunked up membranes, etc.  RO wins out energetically if the electricity is from non-thermal sources (wind, solar, hydro).

Large scale desalination in California?

Okay, so now that we have an idea about how desalination is really done, what would it mean from an energetic standpoint if California tried to fulfill a substantial fraction of its water demand from desalination? I’ll use the approximate value of 20 kWh/m³ (thermal) hereafter.

Let’s start with San Diego’s effort to replace 7 percent of water demand in its 50 MGPD plant. This works out to 160 MW of thermal power. For scale, the San Diego region uses electricity at an average rate of 2.3 GW. So we’re talking a noticeable amount. Extrapolating to 100 percent desalination for San Diego, we get to 2.3 GW thermal, which would substantially increase local power generation demand. Economically, about half of the negotiated $4.80/hcf cost is in energy. It works out to 15 years to recoup the construction cost for the plant under the (poor) assumption of constant prices.

Don Pedro Dam, 1970

What about California as a whole? San Diego county is not a heavy agricultural center, so the problem will get harder if trying to satisfy the state’s needs (and therefore the country’s food needs given the national-scale importance of California’s agriculture). California uses 46 billion gallons of water per day. Supplying 25 percent of this via desalination would require 36 GW of thermal-equivalent power. California runs on 30 GW of electricity, and a total energy budget of 262 GW (thermal; from oil, gas, coal, hydro, nuclear, etc.—according to the EIA). That’s a substantial amount for 25 percent of our water needs.

Another way to slice this problem is to ask what fraction of California’s water could be provided by using the amount of energy that currently goes into pumping water around the state. We use 20 billion kWh of annual electricity for pumping, translating to about 6.5 GW of continuous thermal power. This amount of thermal power could meet 4.5 percent of California’s water needs via desalination. When we currently spend 8 percent of our electricity delivering 100 percent of our water, and would only meet 4.5 percent of our water needs by the same energy investment directed to desalination, we can appreciate the crunch.

Will the Nexus Vex Us?

What a surprise — the world is a complicated place with interdependencies. Is the water-energy connection more than an academically interesting tangle? I think so. Water is undeniably important to our physical survival, and energy is the main physical ingredient in our development of modern society. Shortages in either could have major impacts, and their entanglement means that a shortage in one could trigger a shortage in both. Seems like a problem — especially in light of increasing population pressure and intensifying effects of climate change.

Of course my “solution” is frequently to ask why we need as much energy or water or you-name-it-resource as it seems that we do. The fact that I live a perfectly functional life using less than 20 percent as much electricity, gas, and water as my San Diego cohort sure seems to suggest a viable path away from the crunch.

The good news in all of this is that when faced with difficult limitations, economic factors will assert themselves via the beloved mechanism of skyrocketing prices. People will naturally react by cutting back significantly, as my experience indicates is clearly possible. I am confident that San Diego could still function on a drastically reduced water budget, if needed. Every 60 ft² of roof area in San Diego collects enough rain to provide a gallon per day averaged over the year (1.4 m² collects 1 L/day). So thirst shouldn’t be a problem, even for a few million people. I’m not so optimistic about the odds of grass and ornamental plants surviving serious cutbacks. So while survival is not at stake, our accustomed ways of life may well be endangered.

The bad news is that we appear to be incapable as a society of reacting to a looming situation before economic forces drive us to change. By that time, we have often lost precious years to prepare for a new reality. We tend to want proof that something is a problem before we alter course. Not the smartest of approaches, in my book.

Ironically, the political “conservatives” tend to be the most resistant to conserving resources or approaching the future with a conservative, low risk mindset. Growth trumps caution. A key philosophical difference may lie in one’s sense of whether growth solves problems (debt, hunger, unemployment), or creates them. The answer does not have to be static — especially in a world of finite resources transitioning from the “empty” to the “full” state. We may well see an evolution from a world in which “growth the solution” more and more is perceived as “growth the problem.” I think attitudes are already shifting in this direction.

This post originally appeared on Tom Murphy’s blog, Do the Math: Using physics and estimation to assess energy, growth, options.

Tom Murphy is an associate professor of physics at the University of California, San Diego. An amateur astronomer in high school, physics major at Georgia Tech, and Ph.D. student in physics at Caltech, Murphy has spent decades reveling in the study of astrophysics.

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But additional challenges loom in parallel. Water is very likely to be one of them, which is especially pertinent in my region. For true believers in the universality of substitution, let me suggest two things. First, come to terms with the finite compactness of the periodic table. Second, try substituting delicious H₂O with H₂O₂. It has an extra oxygen atom, and we all know that oxygen is a vital requisite for life, so our new product will be super-easy to market. Never-mind the hydrogen peroxide taste, and the death that will surely visit anyone foolish enough to adopt this substitution. Sometimes we’re just stuck without substitutes.

Substitution silliness aside, water and energy are intimately related in what has been termed the Energy-Water Nexus (see for example the article by Michael Webber from this conference compilation; sorry about the paywall). We’ll explore aspects of this connection here (and in Part II to be published tomorrow), touching on pumping water, use of water for the production and extraction of energy, and desalination. As glaciers and snowpack melt and drought becomes more common in the face of climate change, our water practices will need to be modified, hitting energy right in the nexus.

Household Water

Let’s start at the familiar level. A typical San Diego residence uses 14 hundred cubic feet (1 hcf = 748 U.S. gallons = 2831 L) of water each month—working out to 138 gal/day (520 L/day) per person, assuming an average of 2.5 people per residence. Based on backpacking experience, this is more than one hundred times as much water as is necessary to satisfy basic needs.

Note: only 60 percent of Do the Math readers are from the U.S. The volumetric units in this post will likely elicit a groan or two overseas. Some additional conversions: 1 gallon is 3.785 L; one cubic meter is 264 gallons; and 1 hcf is 2.83 m³.

My own household (two people) averages 20 hcf per year. This past year is slightly anomalous in that we planted a large section of our yard with drought-tolerant California natives, and have supplied 4.25 hcf of water (5.5 inches or 14 cm of rain equivalent) to help establish them in their first year — yes, I record sprinkler use. Even so, our water use over the last year comes to 23 hcf — working out to 47 gal/day (or 38 gal/day ignoring temporary irrigation).

Okay, so I’m shocked² by these sets of numbers. First, I am shocked that we use as many as 38 gallons per day within our house. On what?! We are sparing with showers, each requiring only five gallons and on a roughly two-day cadence. Our low-volume toilets (one of which has a dual flush capability) average something like 1.5 gal per flush, and we don’t flush after every use (of certain types, if you know what I mean). Dishes? Sparing, efficient. Laundry? The same. Vegetable garden? Rainwater catchment (600 gal storage). So it’s hard to get it to add up—yet it must, and I accept that.

The second power of shock (thus the square) is the nearly 10× greater usage (344 gal/day) by typical area households. Yet it’s not an unfamiliar mismatch — also appearing in our use of electricity, natural gas, etc. But where is all this water going?

Presumably, much of it goes into creating green lawns in a semi-arid desert: San Diego typically gets about 10.3 inches, or 26 cm, of rain per year. If I guess that a typical house in San Diego has about 2000 ft² (185 m²) of lawn, then tripling the natural rainfall amount will require 34 hcf of water, or about an extra 3 hcf per month. Hmmm. Not as big a chunk of the monthly 14 hcf as I thought it would be.

Maybe I underestimate how much irrigation people are doing. Overwatering, overspray, evaporation, and leaky sprinkler systems may be a big part of the story, but I am still left a bit puzzled. I guess frequent long showers (also energy-intensive), washing clothes maniacally often, flushing every use, hosing off the driveway, washing cars, etc. may all add up.

One final comment on domestic water. Each month, I pay a $19.33 base rate for water service (not including wastewater service, which is a comparable charge). Then it’s $3.61 per hcf of water used. So my monthly water bill comes to about $26. Meanwhile, the average residence pays $70 for their 14 hcf allocation. I’m paying about 2.7 times as much per gallon as the average resident: my reward for conserving, apparently.

A further amusement is that my water service issued a “20 gallon challenge,” which asks residents to shed 20 gallons per day per person. Setting aside the temporary native-plant irrigation, our 38 gal/day household usage would mean that rising to the challenge would result in our complete abstention of utility water usage. In fact, it would require each of us to cough up (not literally) a gallon of water each month to donate to the utility. Good thing we have rain catchment.

National and Statewide Usage

The USGS provides national water use estimates every five years. For 2005, the total 410 billion gallons per day works out to about 1330 gal/day per person. This drops in half if excluding water used for cooling power plants. For California, 81 percent of the withdrawals were for power plants and irrigation, leaving 240 gallons per day per individual in the state.

Energy for Water

A 2006 report pegs the total amount of water-related energy use in California at 52 billion kilowatt-hours annually. This computes to about 6 GW of continuous power expenditure, or 160 W per person. Not a trivial amount. Of the 52 TWh, 32 are performed by the end user for heating, cooling, moving, filtering, or pressurizing the water. The other 20 TWh goes into pumping water across the state, including over mountain ranges. That’s about 8% of California’s electricity demand!

As a lark, if we dumped all 52 TWh of energy into the annual California water supply (40 million acre-feet: just listen to the Europeans howl), how much would the water warm up? Answer: about 1°C. Not all that much. But it illustrates the degree (ha!) to which water heated by 40°C for a shower or by 80°C for cooking pasta is high-value water, relative to the rest.

Combining the energy and volume numbers in another way, each gallon of water in California comes with an average energy price tag of 0.004 kWh, or 0.0015 kWh for the pumped-delivery charge alone. This means that a 1 hcf unit costs just a bit over 1 kWh to deliver.

Water for Energy

But there is another direction to consider as well. Power plants generally use water as a conveyance for waste heat, and withdraw far more water than any other entity in the U.S. (including agriculture). According to the EPA, every kWh of energy delivered demands the participation of 25 gallons (95 L) of water. Most of this is either returned to the source (warmer by 17°C, I calculate) or preserved in a closed system.

But 2 gallons are lost for each kWh of energy delivered (regionally variable: much higher in arid regions). Luckily, the resulting kWh is sufficient to deliver another 750 gal to the door, so there’s no spiraling trap preventing us from consuming water in this way.

Obviously, hydroelectricity is another place where water and energy collide. In drought conditions, municipalities may increasingly face decisions about whether to use the contents of their reservoir for water or electricity. Interestingly, according to Webber, each kWh of hydroelectric energy produced results in the loss of 18 gallons of water due to increased evaporation off of manmade reservoirs — over-and-above what would have happened in the natural run of the river. So hydroelectricity is more consumptive than the thermo-electric plants by a fair margin.

Production and processing of our fossil energy commodities also require the use of water. Gasoline consumes a few times its volume in water for production. But from an energy standpoint, at 36.6 kWh/gal, every kWh of energy available in the gasoline takes a small fraction of a gallon of water to produce. Thus electric cars turn out to be more water-intensive than gasoline cars, for instance, if each kWh of electricity production gulps a few gallons of water.

For tar sands, the ratio is about 5:1 water:oil-product, plus more for refining. A similar number accompanies oil shale extraction, but in the U.S. the oil shale is primarily situated in arid regions where water availability is limited.

Hydraulic Fracturing (“fracking”) for natural gas appears to require 10 L/GJ of water consumption. For the energy equivalent of one gallon of gasoline, this works out to just about one liter—so not as intensive as tar sands or oil shale, or even gasoline. Mostly this is because gas is happy to flow on its own with little help from water: the water only has to create the cracks (fracks?). However, water does enter the equation in other ways for fracking. Contamination of ground water is a principal concern, and some residents have complained of being able to ignite the effluent from their kitchen sink faucets!

But the real water hog for energy purposes is biofuels. Each gallon of fuel produced may consume something on the order of 1,000 gallons of water (regionally variable). That’s about 25 gallons per kWh, to put it in the same units as we discussed for power plants. Naturally, the impact depends on the degree to which irrigation is employed vs. natural rainfall. I would assume that the amount of water used in the refining/processing is similar to that for gasoline and therefore does not contribute much additional burden.

Stay tuned for the second part of this two-part series, and later this week we’ll publish The energy-water nexus Part II!

This post originally appeared on Tom Murphy’s blog, Do the Math: Using physics and estimation to assess energy, growth, options.

Tom Murphy is an associate professor of physics at the University of California, San Diego. An amateur astronomer in high school, physics major at Georgia Tech, and Ph.D. student in physics at Caltech, Murphy has spent decades reveling in the study of astrophysics.

Image courtesy of JoshuaDavisPhotography, laRuth, Photoctor, dr_relling, RichardBarley, RennettStowe.

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In an announcement on Tuesday, AlertMe — which runs a cloud-based service that monitors and analyzes people’s energy use and gives them detailed feedback — said it had been chosen by British Gas to provide its software to all its customers who have smart meters installed in their homes.

The utility giant has more than 15 million gas and electricity accounts around the country, with more than 10 million households on board. And while British Gas only started rolling out smart meters last year, the U.K. government has mandated that all British homes must be fitted with smart meters by 2020 to help avoid wastage and prevent unnecessary carbon emissions.

“It’s huge for us,” admitted AlertMe CEO Mary Turner when I talked to her ahead of the announcement. “The way I look at it, this is a huge deal for us, and a really innovative move from British Gas — but the important thing is the benefit it brings to the mass market.”

She said that customers would have their smart meters plugged into AlertMe’s energy monitoring service, which takes readings of energy use every 30 minutes and provides a variety of ways for them to drill down into that data. The aim is to reduce usage, cut carbon emissions and (crucially) save money — ultimately providing the benefits of big data to ordinary people in the place that’s most important to them: their own homes.

“There’s been so much talk about smart meters not really being smart, and for the convenience of the utility because they don’t have to pay to send a meter reader around,” said Turner. “But we turn that data into information and insight that’s much more relevant to the consumer.”

AlertMe doesn’t just work with gas usage, however: its platform works with a whole range of sensors and devices around the home. The ambition is for the system to become the backbone of an entire connected home, with an open platform that can deal with data coming from a wide range of appliances — electricity meters, TV sets, washing machines… anything.

We’re still at the start of a trend, but it’s been a good few months for the company. in January it announced a deal with Lowe’s to sell home energy gadets in-store (made by third parties and given the AlertMe seal of approval). And there could be another significant deal in the works in continental Europe, hinted Turner.

The Cambridge, U.K-based company, which has more than $37 million in funding from investors including Good Energies, Index Ventures and Vantage Point Capital. British Gas was already a strategic investor in the company, and had run some trials of AlertMe technology, but the deal was the result of a competitive tender put out last year.

But Turner said she saw this deal as the beginning of the company’s expansion, not its zenith — particularly as consumers look for a way to avoid the mess of standards and services that having a “smart home” entails.

“The fact that we have huge utilities practically engaging with us is a starting point, but our plan is not just to work with utilities,” she said. “We’re device agnostic and we absolutely, fundamentally believe it has to be that way. Walk around your home and you’ll have a dozen brands for all your appliances — the last thing a customer wants to do is have five or six different home hubs managing different devices.”

“Our view is that all of that will ultimately disappear.”

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The round was led by True North Venture Partners, the $300 million fund started by Ahearn and Ahearn will join the Board of Directors of Harvest Power. True North Venture Partners officially launched Summer of 2011 and this is one of the first investments I’ve heard coming from them. Oil refinery firm American Refining and DAG Ventures also participated in the round.

Trash giant Waste Management was a previous investor, but isn’t named in this round on the release. Back in January 2010 Harvest Power also announced a deal with Waste Management to access organic waste (feedstock for its recycling processes) from Waste Management’s operations across the U.S. and Canada, but I’m also not sure on the status of that deal. I’ll update this when I know more.

Founded in 2008, Harvest Power says it’s sold “millions of bags” of organic soils and mulches in 2011 and is in the process of building “two of the largest foodwaste to energy facilities in North America.” The company plans to complete construction of those plants this year, and has been operating seven other smaller sites.

Harvest Power previously raised $51 million about a year ago, putting its total funding raised to over $160 million. The company used part of that money to add recycling technologies, such as a high-temperature process to create synthesis gas. Syngas can be used to produce electricity, transportation fuels and other chemical products.

While Harvest Power Harvest is developing its own technology, it also makes use of others’ know-how. The company previously teamed up with Germany’s GICON Bioenergie to engineer and build processing plants using GICON’s anaerobic digestion technology.

The Wall Street Journal reports that the company — which makes money by selling fertilizer and power, as well as charging waste pick-up fees — generated less than $50 million in revenue in 2011, and expects to generate between $75 million and $100 million this year.

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