The Electric Car Resurrection V: Charging Stations

The biggest issue with electric cars is "range anxiety". Electric cars have a range that is more limited than ICE cars. That would not be an issue if electric cars could be charged up as quickly as ICE cars can be filled with gas. People are used to being able to wait until they are just about out of gas before stopping at a conveniently located gas station, unless they are cruising through Death Valley. With an electric car, it can take anywhere from 25 minutes to 8 hours to recharge, depending on the voltage and current available from the charging station. Most people aren't going to be able to wait 8 hours after running down their 100 mile range Nissan Leaf to zero charge. This will likely take a level of planning most people are unused to, even with iPhone apps with maps of charging opportunities and apps in the car that tell you how much range you have left and whether you could make it to the nearest charging station if you went somewhere.

The simplest solution to the problem is to recharge the car at home. What I do is to simply plug my PHEV Prius into the 110v socket at night, like a cell phone, and let it recharge on cheap, off-peak power. In the morning, it's ready to go again. This type of recharging also works at other places, like a friend's house or overnight at a bed and breakfast, or even downtown at the public library where there are a couple of 110v electric sockets scattered around the garage. After a while, you get proficient at identifying where there are sockets. My wife's employer has two sockets specifically for electric cars that she uses to recharge the Prius. At my employer, on the other hand, the facilities department sent security after me when I plugged the car into an exterior outlet, then put a small sign on the outlet stating that it was not to be used. Oh well.

While overnight charging at 110v 15 amps works for my 5 kwh battery, with a larger battery, such as the Nissan Leaf or Chevy Volt has, the amount of time to recharge on 110v 15 amp would be prohibitively long. Which is why these cars come with a 220v 30+ amp charging station that is installed in your garage when you buy the car (and for which you pay extra). Note that not all houses can support the current load of a high current recharge of this type. If your grid feed is only 100 amps, as many houses are that were build in the 1970's or before, then you won't be able to get an all-electric car without upgrading your grid connection. With the additional current available, an all-electric car like the Nissan Leaf or an gas-assisted electric PHEV like the Volt should recharge in about 5-8 hours, so, again, overnight charging at home works.

This pattern is fine for commuting. But if we want to get away from just using an electric car for commuting, then charging stations need to be essentially everywhere: parking lots, downtown on the street, you  name it. You need to be sure that a station will be available whenever you are in a civilized parking spot (we can leave out Death Valley for now). Not only that, but the car must be able to draw enough current to recharge in a conveniently short time, since people on a 500 mile trip are not going to want to wait 8 hours after driving only part of the way. Making the recharge time the same as it takes to fill a tank with gas is probably too much to hope for, at least initially, but maybe a half hour at most would probably work for many people, especially if the range were high enough, say 200-300 miles like the Tesla. How high would the voltage need to be and how much current are we talking about? Try 400+v at 400 amps, but straight DC instead of AC, and the car would only about half charge in 30 minutes. The conversion to DC happens in the charging station, not the car.

There are a couple startups working on this technology. One is Coulomb Technologies. Their business model is to sell charging stations and the owner then sells the power. Because only utilities, as regulated monopolies, are allowed to sell electricity by the kwh, the charging stations sell power by time. This is a convenient dodge to avoid having the customers of Coulomb be regulated like utilities are. Another startup is 350Green. Their business model is to own the charging stations, install them for free, and cut the property owner in for 5%. Their charging stations also sell power by time, but take time of day and season into account.

Coulomb's model suffers from the chicken and egg problem. As long as there are not lots of electric cars, property owners and municipal governments won't see the economics of buying charging stations. Maybe some gas station owners will install them near areas where there are lots of electric cars, as is the case with E85 fuel. 350Green's model has better economics, though their incentives are a bit slim. Electricity, even during peak times, is about 1/3 the price of gasoline for the same amount of range, so the property owners won't be making much. In any case, there is a technical problem with these fast charging models. Unless the charger contains a large bank of capacitors that charge up slowly to almost the amount of power the car requires, the load on the grid from trying to draw down so much energy over such a short time may cause some failures in transformers and other equipment.

In my opinion, an easier way to solve the problem would be to take advantage of the infrastructure we have. Every street light pole has a small plate near the base the provides access to the wiring. You can see an example here:

What if, instead of installing fancy charging stations, every street light pole was installed with a 110v 15 amp and 220v 30 amp socket? Naturally, this wouldn't take care of drivers going long distances, but it would sure help when you are out driving around on a Saturday afternoon doing errands and need a quick recharge while getting a haircut. The main issue, though, is how to collect money for the power. One obvious way is to put a credit card swipe connected through the cellular network on the pole, and make  people swipe their credit cards. Another would be to have some kind of wireless-based recognition system on the car and pole, and have the pole then charge the car owner through a post-paid plan, like a cell phone plan. There are lots of ways to arrange the charging, municipalities could even sell yearly passes to residents for unlimited power use.

There are probably lots more ways that charging stations could be arranged, but initially, home charging looks like it is most likely to be the initial pattern. This isn't actually so bad, since many families have at least one car that they just use for commuting. If a large majority can be convinced to replace that car with an electric, the impact on carbon emissions will be huge and we'll be well on our way to permanently reducing our collective carbon footprint to where it doesn't threaten the planet.

The Electric Car Resurrection IV: Plug-in Prius Conversion

As the the Deepwater Horizon sinking slowly destroys the Gulf of Mexico and the consequences of our addiction to carbon-based energy go from being diffuse and hard to see to painful and in our faces, I though I would continue the Electric Car Resurrection series with a post about our plug-in hybrid Prius conversion.

If you've been following the series, you'll remember from this post, admittedly some time ago now,  that after studying electric cars for 3 years, I was really ready to go electric. At the time, we had a 2002 Prius that was averaging around 42 mpg and a 1996 Corolla that was averaging around 30 mpg. I was really motivated to replace our 1996 Corolla with something that I could plug in to reduce our carbon footprint. Also, I figured we could get some of the power free from our solar PV since we regularly gave back around $80-$120 per year to PG&E in unused credit (though we did use around 1000 kwh from the grid so we were not 100% carbon  free). Despite all my investigation, I hadn't found an electric car option that would really work.

In the spring of 2008, A123 announced their plug-in hybrid conversion package for the 2004-2008 Prius, the L5 plug-in hybrid conversion module. The details of the package looked pretty good. The conversion removes the spare tire and installs a 5 kwh booster battery in the spare tire well, along with a traction battery charger, and a 12v battery charger to handle the increased load on the 12v battery from the electronics in the booster battery. The booster battery uses a technology which A123 calls "lithium nanophosphate", in reality, it is their proprietary development of the lithium iron phosphate technology. This technology is reported to  be exceptionally stable and  long lasting, unlike the lithium cobalt technology used in laptops. A123 had pictures on their Web site of crash tests in which the batteries simply crushed along with the rest of the car, instead of exploding or anything like that.

The 5 kwh battery is connected in parallel across the 1 kwh OEM battery, and it trickle charges the OEM battery, which means that the 5 kwh battery does not recharge from the regenerative braking. Because the basic drivetrain power equipment is untouched, the warranty for the drivetrain is not voided. In fact, several Toyota dealers in the mid-West offered the A123 plug-in conversion as an option. The battery management system in the booster battery interfaces with the CAN bus, and the state of charge for the booster battery is smoothly integrated into the Energy screen on the car's flat panel display. The booster battery appears as an overlay second battery on top of the OEM battery and the display flashes between the two so you can see the state of charge in both.

While the car ends up not having a spare tire, it isn't a practical problem because the tires are all equipped with slow leak detectors, so as long as you stay on top of any reported  leaks, the only problem could occur with a blowout. With that, you of course need to call a tow truck. Alternatively, you could take  along a can of the inflator goo that re-inflates the tires and seals the leak, but that also destroys the leak detector, which is somewhat expensive to replace. Other than that,  there didn't seem to be any drawbacks or negative  impact on the car.

So we decided to do a conversion. The first step was to locate and buy a 2008 Prius. I wanted a model with everything but nav system (I can get that from Google maps on my phone or a paper map), silver in color. If you recall, spring 2008 was the peak of gas prices,  where gas was going for $4.00 a gallon here in California, and Priuses were selling like hotcakes. I had a hard time locating a car, most dealers were sold out with 6 weeks  to 3 months waiting time. However, I did find one,  but unfortunately it had been used by a salesman and had 3,000 miles on it. I tried to argue the sales guy down (it was really used car) but he would have none of it. Priuses were hot items and he knew he could sell it elsewhere for full list price.

I bought the car in May 2008, then we waited. A123 was having some problems with CARB getting the license for the conversion. One little known fact about converting cars to use something other than the fuel they originally come equipped with is that it is illegal  without an EPA and, in California, CARB license. The licenses are difficult to obtain, cost upwards of $24,000, and only apply to a specific make and model of car. This is one reason why you don't see many conversions to E85 (in addition of course to the lack of stations selling it). There are very few companies that are licensed to do legal E85 conversions (and most of those do ancient Dodges and such), any others - including those done by hobbyists - are illegal. The ostensible reason is because EPA wants to make sure that the converted car doesn't pollute any more than the original, and that in fact was the holdup with the A123 conversion. EPA was afraid that the catalytic converter wouldn't get hot enough because the engine doesn't go on much and so therefore the car would pollute more. A123 was finally able to satisfy them, and in October 2008, A123  started notifying people who had signed up and paid their deposit when their installation date was.

In November we got a notice saying that our L5 conversion package would be shipped to Pat's Garage in San Francisco shortly. I took the car up to San Francisco when it arrived and they had the L5 conversion installed in about 4 hours. Pat recommended to me that I get a set of sports car shocks installed in addition, because the original squishy shocks that come with the Prius tended to wear out under the additional 200 lbs of battery. I took his advice and, I must say, I am perhaps even more pleased with the shocks than with the electric conversion. Toyota's shocks are almost uniformly squishy, but these shocks make the car feel like a BMW. The shocks cost an extra $1K but they were really worth it. If I ever buy a Toyota again, I'll probably have them replace the shocks. In addition, a few weeks after the conversion, Pat told me about the need for an extra 12v battery charger. If the 12v battery goes out in the Prius, you can't simply jump it like in any other car. You must tow it to the dealer and have them replace it. Since the L5 electronics about double the load on the 12v battery, I thought it prudent to have the 12v battery installed.

Below you can see the back of the car with the electric socket and an extension cord plugged in in our garage.

We had the car decked out with decals on the back bumper and side.

Here's an overview of the booster battery pack:

And this shows more details of the battery pack, including the ventilator that keeps the battery cool:

The ventilator is the black plastic box across the middle of the picture. Normally we also carry a 25 ft. extension cord for "opportunity" charging. Many places will let you plug in for a couple hours, or even overnight if you are traveling longer distances.

The installation also includes a switch on the dashboard for switching the booster battery on and off, and a red light that glows when the booster battery is on and charging the OEM battery:

When the car is plugged in, the back tail lights go on for about a minute, then switch off.  Originally, the lights stayed on while the car charged but about a year after the battery was installed, the car got a software upgrade that fixed that and another  problem, involving the inability to go into electric mode. If you try to push the acceleration sometimes below 33 mph, the car starts beeping and the display says that it can't go into EV mode. This problem occurred frequently on the original software, especially on steep hills, now it has been improved to where it almost never occurs.

The original specs for the battery pack promised 30 mi. all electric range after maybe 5 min. of standard hybrid drive in order to burn off any evaporated gas vapors and heat up the catalytic converter. A standard 110v 15 amp house current socket is sufficient for charging, so no need to install a specialized 220v recharging station. Recharging takes about 5 hours. While the booster battery still has charge, the car remains in EV mode up to 33 mph (60 kph). In EV mode, the car only switches on the engine if the amount of acceleration needed is large, much larger than causes the motor to cut in in hybrid mode. But above 33 mph, you really need to work to keep the car in EV mode even if there is still sufficient charge in the booster battery because the engine cuts in more often (though not as often as if only the OEM battery is providing power). In practice, the car really only gets around 20-25 mi in all electric range before the booster battery is exhausted but that is enough to get me to work and back with a side trip to the gym for a workout.

You'll also notice the decal for the PulseStar spark plugs on the back of the car. If you read my previous posts (here , here, and here) you'll remember that I had the PulseStar plugs put into my 2002 Prius and that they shorted, destroying the ignition coil. But the company paid for the work on the car and gave me a discount on new plugs, so I bought a new improved set for the 2002 Prius. I also  installed them in the 2008 Prius around the time I put the first set in the 2002 Prius. So far, I've not had any problem with them. With no booster battery, the plugs increase the gas mileage around 2 mpg or so.

With mostly around town driving and an occasional trip to San Francisco, Yosemite, or Monterey, the car gets a long term average of around 80 mpg, 30 mpg more than the EPA combined rating. The first six months we had the car, we tried to push the  mileage as high as we could, with hypermileing maneuvers like driving slowly to keep it in electric mode, and we never took it out of town. We were able to get the mileage up above 100 mpg (actually, it was around 110 mpg as measured from gas consumption, the in-built meter won't measure higher than 99), but as soon as we took a trip to Yosemite it dropped.

Despite the fact that the car doesn't get the advertised range, I am still more than pleased with it. We don't fill up more than once every month and a half if we just drive it around town, and most of our driving is around town. Assuming we keep the car 10 years and drive about 8,000 miles  per year (lower than average, but about what we usually do), the cost of the eliminated carbon is around $1.36 per kg of carbon eliminated. The initial upfront cost of the system is somewhat steep, but during the same 10 year period we end up saving around $8000 in avoided gasoline cost if gasoline is $3.00 per gallon (about what it is now). Since we get the electricity for free from our solar PV system, we don't have to pay for electricity either. This will not pay back the cost of the conversion, but, on the other hand, it will not break our bank account either. We could have chosen to buy a luxury car like a Lexus that cost about the same as the plug-in Prius, but then we would have had to pay for gas on top of the carbon pollution, and we would be contributing to the kind of consumption that leads to incidents like the Deepwater Horizon.

The Electric Car Resurrection III: Are NEV's the Answer?

"NEV" stands for "Neighborhood Electric Vehicle". NEV's are a relatively new class of electric vehicle that evolved out of golf carts. They are street legal but are restricted by the National Highway Traffic Safety Administration to run under 25 mph, though many states allow them to drive up to 35 mph. Below is a picture of an example NEV, the Zap  Xebra:

The specs on this car are:

• Speed: up to 40 mph
• Range: Up to 25 miles per charge
• Cost: around $12,000 before taxes
• Battery: Lead Acid

The idea behind NEVs is that many people do most of  their driving around town for which they don't need a full sized ICE vehicle or even a hybrid/plug-in hybrid. In that kind of situation, the range and speed limitations don't mean as much.

Bruce England, a colleague who I met through some work we both did for the local city-sponsored sustainability effort, bought one in 2008 (he reports about it here). He uses his Xebra about 99% of the time and really loves the car. But there are many drawbacks. The only safety feature of the car is a seatbelt (and see here for what may happen in a crash, even at low speed). Bruce doesn't seem to find the range restriction such a problem, though, for me, it would be just on the border of what I could use for a daily commute if I were not going anywhere else during the day. Battery maintainability is an issue even with lead acid batteries, and Bruce recommends a couple of after market battery maintenance devices, since the Xebra does not come with one. Lithium batteries absolutely require a sophisticated battery maintenance system or else they can be easily ruined by overcharging, which of course makes them even more expensive but more robust. Lead acid batteries can last up to 10 years depending on how they are used, but they can also quickly expire after 3. Replacing batteries can be expensive and easily negate the cost advantages of electric over ICE. Bruce also has a list of creature comforts and fit-and-finish features that are taken for granted in cars from larger manufactures, but are missing in the Xebra.

The main issue with NEVs is that they are a low volume product so they are much more expensive than a mass market car, independent of their electric drive. Zap has a little more than 700 vehicles on the road compared to the hundreds of thousands of Priuses. The cost per mile of range for the Xebra is about 8x that of the Prius, and is even about 1.5X  more expensive than a list priced Nissan Leaf (if you include the CA state and federal subsidy, it is around 2.4x). If they were to feature the same price/performance ratio as the Prius, the Xebra would cost around $1400, which is much cheaper than a Tata Nano. A Leaf may be a better comparison, that would be around $8000 based on the list price. If you are satisfied with 25 mile range, lead acid batteries, only 40 mph top speed, so-so creature comforts and downscale fit-and-finish, you are probably better off buying a used Geo Metro for a couple of grand, and converting it  to electric yourself, or finding someone handy with tools like my friend Steve to convert it for you.

Some Whining + System Remodel Gas Pipes and Insulation

I haven't posted for a while. Basically, I'm starting to lose motivation in this blog, plus I am working on another writing project which is really engaging but is taking up all my computer time. It seems people really don't care much about green technology judging by the number of comments I'm getting. Michael Kanellos over at GreenTech Media has an excellent article about why there will not be a Google of green tech. On the other hand, today, I went shopping at an Apple store today to buy a Mac for my nephew, who is graduating from high school. It was packed. Families with kids, people poking around at the gadgets, all in response to the unceasing hype around the iPad. Maybe I ought to start a blog shamelessly promoting Apple products.

It kind of reminded me of how people used to flock to car dealerships when the new cars came out in September during the 1960's. When it comes to stuff that doesn't matter, people seem willing to pay lots of money and spend a lot of time with it. I can't imagine that anybody would bring their kids to a store to check out geothermal heat pumps or solar panels. Meantime the defunct oil platform formerly known as Deepwater Horizon is spewing pollution into the Gulf of Mexico at a disputed number of gallons per day, threatening their next shrimp cocktail. It baffles me why people can't make the connection between their lifestyles and the massive environmental degradation that is taking place before their eyes.

Anyway, I'll try to get back to my series on electric cars with a post next week. I just reserved a Nissan Leaf. While I have some reservations about electric cars (which I hope to blog about if I can dredge up the energy), the prospect of fulfilling 95% of our family's daily transportation needs from solar electricity off our roof, plus the fact that California grants free carpool lane access to electric cars was too tempting to pass up. On top of that, after federal and state tax rebate, the Leaf should cost less than $20,000, cheaper than a Prius.

I also expect to be posting more frequently when our system remodel starts. Right now, the geothermal HVAC design is underway. Forrest, our architect, came by today and did some measurements of the gas pipes, and recorded what insulation we have in the walls currently, for Title 24. I couldn't understand why he wanted the gas pipe lengths, since we will be taking out the gas hydronic boiler and hot water heater. He mumbled something about the city needing the number of BTUs going into the house now in order to grant the permit. Perhaps they are starting to get serious about actually measuring carbon emissions, and want to know how much our system remodel will be eliminating. Though that may be too much to hope for. Forrest said that they have been requiring this number for commercial remodels for a number of years.

He also measured the distance for the new gas pipe that will go in for the gas fireplace. The gas fireplace will be replacing an old pellet stove that doesn't have a thermostat, needs to be hand started, and which we haven't used since we moved into the house  because it is too fussy. I am not thrilled about putting in a gas fireplace, since it is not consistent with our goals of making the house carbon neutral. I wanted to put in a newer pellet stove which has automatic ignition, a thermostat, closed combustion firebox, and low particulate pollution. But there is a moratorium on wood burning appliances for the entire Bay Area, regardless of the efficiency of the appliance, due to the severe particulate pollution that develops during winter inversions. We could get an alcohol burning fireplace, but it seems even more fussy than the pellet stove. You have to fill it with alcohol (which will naturally spill) and light it, and of course it also has no thermostat. Though it would work during a power outage from an earthquake, which is not the case for a gas fireplace. The gas fireplace we are thinking of installing is around 90% AFUE, closed combustion, with thermostat, and generally the most efficient on the market. We're already signed up for carbon credits with PG&E, and, besides, we  were not planning on replacing the gas kitchen stove, so we do need to continue to have gas service.

Why are we not replacing the stove? Well, gas is actually somehow easier to cook with than electricity in my experience. I've used an electric stove before and I don't like it as much. I've found it is easier to burn stuff. Electricity is certainly better for ovens, and we do have an electric oven (and of course a microwave) because it gives more even heat. I think we may ultimately replace the gas stove with an induction stove, where the stove top doesn't get hot, when we get old enough that burns become an issue. Burns from stoves are a leading cause of injury in elderly people. Besides, the stove doesn't use much gas, just one therm a month, based on our gas bill from last summer when we had everything else turned off. That should easily be offsetable with carbon credits.

On the insulation, Forrest said that we may be eligible for a tax credit if the insulation reduces energy use by 20%. Perhaps this is a state credit, because, to my knowledge, the feds are still only giving out $1500 per year for insulation. From what I have heard, the "Cash for Caukers" bill passed the House, but, as usual, is stuck in the Senate. The Senate doesn't seem to hold energy at a high priority, so I kind of doubt it will be approved before we start the remodel. I think we will probably achieve at least a 20% reduction. Some years ago, I did a detailed spreadsheet on the heating energy usage of the house, based on the existing insulation and geometry, and how it might improve under various new insulation treatments. For the kind of treatment we are planning (basically R-6 per inch closed cell foam on the ceiling and all outer walls with exception of the master suite and one kitchen wall) the improvement was something like 30%. In addition, we are also planning on replacing the fiberglass batting under the floor with closed cell foam. I didn't include the floor in my spreadsheet, so we may get a somewhat higher reduction.

On Again

Forrest arranged for us to visit a house he is working on with a heat recovery ventilation (HRV) system, so that we could get an idea how noisy HRV is. On Friday, we drove up to the place. The house is a job that Forrest has almost completed. There are still a few items yet left to finish, and the owners had graciously consented to let us check the HRV out since they are away.

Surprisingly, the HRV system is almost silent, even on the highest setting. The only time I could hear anything from it was when I was standing directly under the vent in the bathroom, and that was just the sound of the air coming out of the duct. Forrest also turned on the forced air furnace, and that was much noisier, I guess because the amount of air being pushed through the ducts is larger.  Paul, Forrest's partner, opened the attic and let us take a look at the HRV in operation. With the attic door open, you could hear a distinctive hum, but the vibration was not transferred to the structure of the house, unlike a forced air furnace, because the HRV is mounted from chains connected to the frame of the house with springs. This acted as a sound damper, removing any vibration. Sound propagation through the HRV ducts is also limited by putting in lots of right angle turns. These break off the paths through which sound waves can easily propagate.

We still have some concern about the geothermal heat pump. The big pump that sends the heat exchanger fluid into the ground and the compressor that either extracts the heat from the fluid or puts it in are both likely to generate vibrations. Just like a forced air furnace, they can't be hung from the frame of the house because they are too heavy, though there are some measures that can be taken to isolate the heat pump from the frame of the house. We discussed putting the heat pump in the garage and running an insulated line to the heat exchanger in the mechanical closet instead of mounting the heat pump in the mechanical closet. We need to have the heat exchanger in the mechanical closet because that is where the manifold is for the radiant heat system. Of course, we would also need to figure out how to engineer the air conditioning. The air conditioning is never likely to be quiet, since, just like a forced air furnace, it will be shoving large amounts of air through the ducts. Putting that in the mechanical closet seems unavoidable if we will be using the old forced air ducts for air conditioning. They all converge on the mechanical closet because that is where the old forced air furnace was, though the ducts that were under the house have been removed and will probably need to be replaced.

I also asked Forrest if we could connect the air conditioning to a ventilation system with a heat exchanger. This would allow us to get fresh air into the house in summer through the air conditioning rather than opening the windows or running the HRV. He said that this typically isn't done, that the warm air return for the squirrel cage blower on the air conditioning comes from within the house, just as with a forced air furnace. In fact, the air conditioning (or forced air furnace if you have that) and the HRV are two separate sets of ventilation ducts. Somehow, one would think that somebody would have been smart enough to combine the two.

I continue to be amazed about the lack of efficiency in planning HVAC (heating, ventilation, and air conditioning) systems. Stuff that seems obvious to me as an engineer with a systems orientation never seems to have crossed the minds of the people who designed these systems. Every function is in a separate box. It is no wonder that over 40% of the energy in this country is used by buildings. Without proper integration of these systems, there is redundant energy use. For example, the squirrel cage blower on a forced air furnace and the HRV system are essentially doing the same thing: pushing conditioned air through ducts. Why not combine them, and run the cold air return through a heat exchanger on the furnace and out, and draw in outside air through the heat exchange and into the furnace?

Anyway, we've told Forrest to move ahead with the geothermal planning. We signed the design contract two weeks ago, but put it on hold pending an opportunity to experience how much noise an HRV system really makes. This means the final design will be pushed out by at least two weeks (and if we are lucky, only two weeks), meaning the start date is likely to be late June. Four months puts us into October. If the project is delayed (as usually in is the case in my experience) we could end up moving back in around Christmas. Considering we are planning on living in the back bedroom and also mostly outside during the summer, things could get a little tight come October when the weather starts to get cold again.

One Slice of Bread

Today I got a letter from PG&E telling me that they had decided how much they will pay me for the extra power my solar PV system generates, above what I use, starting next year. A couple months ago they sent a letter saying that they would start paying their net metering customers in 2011 at the annual true-up date. Up until this year, our solar PV system has been generating between $30-$134 more in credit than our house consumes. We kind of viewed at as our contribution to greening the planet since it hasn't been all that much.

The house isn't carbon neutral, though, we use around 1000 kwh/year more power from the grid than we generate. The difference is that we generate more power during the summer in the afternoon and evening than we do during the winter and in the morning. Due to time of day metering, PG&E pays us around $0.30/kwh for summer solar-generated peak power but only charges us around $0.09 for offpeak and winter power. It's a pretty good deal for us all things considered, though it wouldn't be if we had to use air conditioning during week days in the summer. We get the favorable rate because the folks in the Central Valley need to have their air conditioners on all day. So they use more power during the peak.

In their letter, PG&E proposes to pay its net metering customers $0.08/kwh for credit they incur above what they use. They claim this is consistent with the California Public Utilities Commission mandate in AB 920 (the law that requires net metering customers to be compensated for unused credit they incur) requiring the compensation to "set the rate for generation, including renewable characteristics, without shifting costs to other customers". I have a bit of trouble seeing how their math works out. If the power is worth $0.30/kwh to them in the summer, then how does it suddenly become worth only $0.08/kwh when they need to pay me hard money for it instead of trade? It's not like they don't have the information in their billing systems about when I generate the power, they could easily prorate the reimbursement based on time of use metering, just like they do with the cost.

The larger issue here of course is that such measly reimbursement rates aren't likely to encourage homeowners or businesses to install more solar. But this has been consistent with PG&E's position all along. The reimbursement rates quoted in their tenders for renewable energy systems over 1 mw a few years ago were similarly unattractive for investors, and they were fixed for 20 years. Contrast this with Germany and Spain, where feed-in tariffs for renewable power 3-4x fossil-generated power, set for 30 years have seen an explosion of investment in renewable systems. The net metering reimbursements are a kind of feed-in tariff, but not a particularly attractive one for individual investors, such as myself, who would like to maximize our solar generating potential but also earn some money on it. PG&E has been happy to provide net metering in trade, but when it comes to paying real money for distributed, small-scale power generation, well, that's another story.

I probably shouldn't complain, since the credit is actually just a mathematical construct due to PG&E's tariff structure. In the spirit of "half a loaf is better than none", I guess I'll take this slice of bread they're offering with gratitude, and hope the State Legislature and PG&E figures out some other way to encourage more solar.

Noise

Last week on Wed. we had a meeting with Forrest, our architect, to discuss the geothermal design contract. The contract had a lot of assumptions about our situation that weren't true, but Forrest said that his experience with the company was generally good, except for the design contracts. They tended to do this - put lots of irrelevant stuff in the contract - just to make it look more precise, though, actually, since it didn't correspond to our situation, it made the contract look inaccurate. We decided to take his word for it and go ahead with the design.

Later in the meeting, we reviewed a list of items that I have been accumulating. One of them involved soundproofing the geothermal heat pump and HRV system to ensure that they do not generate a lot of noise. Forrest told us that the HRV systems were, in fact, noisy but that there were measures, such as bending the pipe 90 degrees at the vent, to reduce propagation of noise from the HRV unit to the vent, although sometimes this couldn't be done. HRVs are mechanical ventilation and anybody who works in an office building knows what that sounds like. Basically you are working with the sound of a fan running in the ceiling all day as the accompaniment to your creative thoughts. Forced air heating sounds the same way.

Our house is particularly susceptible to noise, since it was built in the 1970's and there is nothing put into the structure to inhibit vibrations from one part of the house - say, the running fridge in the kitchen downstairs - from propagating to another - say, my office upstairs. When we had radiant heat put in a few years ago, we were astounded how quiet the house became in winter. It's not that you can't hear anything, the furnace still makes a low frying noise from the burning gas, it is just much quieter than having a squirrel cage blower whaling away in the mechanical closet, and the sound of the air whooshing out the vents. There's also the almost inaudible sound of the solar hot water pumps usually in the afternoon of sunny days, and, of course the fridge. But all these add up to very little noise, and the noise is also intermittent. With tightly insulated houses, the HRV system must be on all the time, otherwise the air quality inside the house suffers.

I found this a little hard to understand, since the German Passivhaus standard requires HRV. Passivhaueser (in German, "passive houses") are basically so tightly insulated that they require no supplemental heating beyond that from the appliances (like the fridge) and people within them, even in the cold German winters. An HRV system takes fresh and possibly cold air from outside, circulates it through a heat exchanger with stale air from inside on the other side of the heat exchanger, and exhausts the fresh air into the house and the stale air to outside. In this way, the occupants get fresh air but the heat is retained. Our insulation would not be that tight, since we have the solarium on the back that probably leaks heat and air, and also, we are not reinsulating the master suite nor one wall in the kitchen, but nevertheless, the amount of insulation we are putting in is enough that it could cut down on the amount of air infiltration sufficiently to allow air quality to suffer. We already have a problem with cooking odors lingering into the next day.

Now Germans are particular about noise in their houses. Even regular German houses are very solidly built in comparison to American houses, usually from ceramic bricks shaped like cement blocks, and they have heating systems that run on oil or gas that either use radiant heat as we do or radiators under windows. American houses are flimsy in comparison. All this mass makes for a very quiet house indeed, very little traffic noise penetrates. So I found it hard to believe that HRV systems could be noisy, the Germans who are now building lots of Passivhaueser, would never stand for it.

Naturally, I went on line to try to figure out what the problem was. In particular, I wanted to find out how much noise HRV systems emitted. The specs for the unit Forrest recommended had no noise rating. But - surprise! - the same thing was true of every single unit manufactured in the US or Canada that I looked at (and I checked 10)! The only unit sold it the US that had a noise rating was the Panasonic WhisperQuiet(tm), which is made in Japan. The WhisperQuiet is actually a bathroom ventilator, because it exhausts directly out of the unit rather than through a duct, so it is unsuitable for our situation, but the noise rating (though in an unusual measurement) was quite good.

Even more surprisingly, every single unit manufactured in Germany and sold in the other countries of the EU had a noise rating on it! The quietest I found were products manufactured by Paul Lueftung. There are various models, but the noise rating ran from 18 db to around 33 db. This is about the amount of noise in a quiet room, and these units are in fact used in Passivhaueser. Products from other companies typically started at 35 db. Unfortunately, the units conform to the European power standard - 230V/50Hz. In the US, we can get 220V which is probably OK, but 60Hz which might be a problem for an AC motor. The units may have DC motors and a power supply, in which case, we could convert them to our power standard. I need to look into this as a possibility.

It seems rather strange that the US manufactured products don't come with a noise rating. Don't Americans care about noise? I guess not since they put up with noisy forced air heating and noisy ventilation in offices, or maybe the sound of all that electricity being used makes people feel like Progress is happening. But I suspect the answer is much simpler: the German government requires manufacturers to include noise in their technical specs whereas the American government doesn't. Guv'ment regulation! The German technical specifications were also considerably more complete and prominently available on the manufacturer's web sites. In several cases, it was difficult to find the American manufacturer's specs, and they were quite skimpy, for example, the noise rating was listed as "quiet".  Of course, your "quiet" might be my "noisy", a db rating is much more objective.

I also looked briefly into noise from geothermal heat pumps, there the situation was the same. Lots of web sites talked about how little noise they generated outside, in comparison to air source heat pumps, but nothing about the actual noise generated by the heat pump itself. I figure that there are three components to noise from the heat pump: the pump circulating the heat transfer fluid into the ground and out, the compressor, and the forced air system (if the system is forced air). On heat mode, our system won't have the latter since we use radiant heat, but we would have the first two. On air conditioning mode, of course, we would have to put up with all three, but there is nothing we can do about that, it is not possible to use a radiant heat system for cooling. I figure that the compressor can't be much noisier than a fridge and the heat transfer fluid pump should be about the same as the solar hot water pumps, but then who knows? A fridge we got in our old house was so noisy that we got rid of it after a couple years, we could not afford to do that with a heat pump. The heat pump will probably have to be American manufactured because the electrical system is probably too complicated to convert,  so it could be bad.

Anyway, we asked Forrest to hold off on the geothermal design and the HRV design until we get more clarity about this issue. In the worst case (i.e. we can't get a quiet HRV system), we can back off the insulation and  just do under the floor (where the current fiberglass batting causes lots of radiant heat to leak in to the crawlspace) and on the central hallway ceiling, which must be replaced due to cracking, then we probably don't need HRV.  As for the geothermal,  maybe we could mount the compressor and heat transfer loop pump in the garage, and the heat exchanger in the mechanical closet. Or possibly get some kind of soundproofing under the compressor so it doesn't shake the floor.