Brief Thoughts on Nissan Leaf EV

So Nissan announced their EV for commuters – the LEAF EV. 100 miles (spec.) on electricity. So what makes this stand out over all the other EVs being offered or promised?

First, the most interesting thing I saw was the 50kW DC charger. This is incredibly useful from a commuter standpoint – if you’re on your way home from work and need to run some errands, if you plug it in for 10 minutes you get an extra 30 miles, which will probably get you anywhere you need to go in your city.

Next is the that the electric motor is capable of 80kW (106hp). That is low compared to the Volt’s electric motor is 111kW/150HP, and the LEAF is estimated to weigh about the same (3,300-3,500lbs) as the Volt – as the extra 8kWh of batteries are about the same weight of the Volt generator. I’ll be interested to see acceleration and highway performance of the LEAF once they start to do road tests.

Overall, I don’t think they’ll hit their 100 mile range target, even the current Mini-E owners are saying that their real world mileage is about 70 miles per charge despite promises of 100 mile range. Not that 70 miles is bad, but there might be the occasional time where something happens and you end up exceeding 70 miles in a day. This is why its imperative that the same working group that did the SAE J1772 connector start work on a high capacity off-board DC charger. Up to 50kW is probably enough, assuming the 20-30 miles per 10 minutes figure holds up. Not all batteries will be able to handle that (E-REVs and plug-in hybrids wont be able to charge that quick) but if they could dial it down to what they could accept (15kW, 6kW, etc) it would allow more “charge point” and “service station” type places to recharge your electric car.

GM Promises Full 40 Mile Range at the End of 10 Years

In a recent online chat, when asked by a member of the public, GM stated that the Volt will have its full 40 mile range for the warranty period of the battery (10 yrs/150,000 miles). How will they manage that?

The Volt’s battery is 16kWh, with 50% of the capacity (8kWh) used to propel the Volt the first 40 miles. So how does GM guarantee that it’ll last that 40 miles for the full life of the vehicle? Well, as the total capacity decreases, the Volt can still pull 8kWh of energy from the battery. There are a few issues with this approach however.

First is that the maximum amount of power you can draw from a battery at any given moment depends on the state of charge (SoC) expressed as a percentage of total capacity. Generally speaking, you have a higher maximum power when the battery is fully charged and as the SoC decreases, the maximum power you can draw goes down as well.

This plays into how battery deterioration works over time. A battery’s total capacity will drop over time (both calendar time and cycle count), and that 8kWh needed to power the Volt for 40 miles will go up from 50% of the total capacity. As that percentage goes up, the Volt will need to expand its 50% depth of discharge to get 40 miles. Out of the factory, the battery will discharge between 85% and 35%. However if total battery capacity would degrade over 10 years from 16kWh to 13kWh (roughly 20%), then the depth of discharge would be 61% instead of 50%. We can assume the pack would go from 90% to 30% SoC, so as the battery charge state goes below 35% the pack will be able to produce less power. The issue is how much.

Could this mean that over time, battery only mode (aka Charge Depletion mode, or CD) will have decreased performance? Will 0-60 times, top speeds, etc remain constant over the life of the vehicle? GM would need to build these margins into the battery pack out of the factory, which is currently a large set of unknowns (though GM’s battery testing facility will certainly help answer these questions).

The other factor that plays into this is the cycle life. If the battery is limited to a 50% depth of discharge (DoD), the cycle life will improve dramatically over the 100% depth of discharge bench test. If a battery can go 750-1000 cycles at 100% DoD before losing 20% of the original capacity, the battery can likely take 3 times as many cycles at a 50% DoD (Motorola states that Li-Ion battery cycle counts increase exponentially as DoD decreases from 100%). GM will likely need a maximum of 3,750 cycles (40 miles each) to reach 150,000 miles, though its likely actual battery cycle counts will be closer to 3,000 in real world use. Anyone recharging the battery twice a day (recharging at work for another 40 mile drive home) will likely run up against those cycle counts much sooner.

As a risk to the program and to GM, I think the risk is fairly small. By the end of 2010, GM will have had its battery facility open for over a year. Their ability to test batteries in the worst of environments and to test cells, modules and packs and rack up the cycle counts quickly. Even if GM were forced to replace batteries after 7-8 years for those vehicles in the harshest climates (desert southwest, cold northern climates), the prices of batteries by the time 2018 or 2019 rolls around will be much cheaper (as much as 70% less than the 2010 price) and GM could even monetize the replacement if they offer a discounted upgrade battery (though I don’t know if that’s kosher/legal).

Lithium Carbonate Supplies Abound!

One of the worries I often hear about opposition to electric cars is that we’re trading one resource for another – oil for lithium. The list of countries with large lithium deposits aren’t overtly hostile to the US and its allies, however they are further left than we are (but who isn’t really?). Evo Morales of Bolivia has already stated he didn’t want outside companies to come in to Bolivia and take the lithium. But do we have enough from other sources to provide the number of lithium-ion batteries we’ll need to power the cars of the future?

An article at Seeking Alpha discusses a lithium conference held in Chile this year. At this conference, the future of lithium demands and reserves were discussed. The geologist who authored the article estimates that there are 30M tonnes of elemental lithium and 160M tonnes of carbonate (Li2CO3) – the actual material used in the production of lithium ion batteries.

Beyond that, there is a fairly high confidence of accuracy of these claims. Drilling performed in a mine along the Oregon/Nevada border indicated that an estimate from years ago was within 10% of a recent drilling. Western Lithium is focusing in on a single deposit of lithium of around 770,000 tonnes (1.5B lbs.) in Kings Valley, Nevada, with an estimated 11 million tonnes total (25B lbs.). With the recovery estimated at 85% for this area, that’s 9.35M tonnes of carbonate. They estimate producing 20,000 tonnes of LCE per year by 2013, and at a rate of 0.6kg/kWh of battery, it is enough for 3.3 million 10kWh battery packs per year. The most recent peak in the 1990s there were only 8.7M passenger cars sold (not including SUVs, trucks, etc), so a 10kWh battery coupled with sufficient technologies to allow 40 miles per charge (increased power/kg, depth of discharge) would allow 38% of cars manufactured to be PHEVs if the market and prices allowed, and this is just from one site located in northern Nevada, accessing only a fraction of what the site is expected to produce.

Down in southern Nevada near Tonapah, there is the only existing lithium brine recovery operation in the US in Clayton Valley, Nevada, where estimates range from 2 million to 20 million tonnes of LCE. One more valley over, there is the Fish Lake Valley, which has similar concentrations of lithium as Clayton Valley. The Clayton Valley site currently produces 5,700 tonnes annually, or enough for about 594,000 16kWh battery packs per year – the first three or four years of Volt production wont exceed 250,000 units. And I still haven’t left the great state of Nevada.

So what does 160M tonnes of lithium carbonate equivalent (LCE) equate to in batteries? With current production techniques, 0.6kg of lithium carbonate will be used per kWh of battery storage capability, and 1 kg of lithium carbonate is equivalent to 0.1875 kg elemental (pure) lithium. At 0.6kg LCE per kWh, recovering 50% of the estimated 160M tonnes of LCE would result in 13.3 Billion 10kWh batteries, or 3.8B 35kWh battery packs for battery electric vehicles. There are about 1B vehicles on the planet now, and factoring in growth to 2B by 2030, it would take about 60 years to go through that amount of lithium (assuming batteries last 10 years). When you combine this with lithium recycling, the supplies are enough to last us well until we find the lithium-ion replacement technology.

So what about recovery? Even by 2030 when plug-ins and pure electric cars are 90%+ of the sales (as estimates), that would mean an annual US vehicle production of 12 million vehicles per year would require almost 11M vehicle battery packs, at an average of 15kWh each, that’s 165 million kWh, or 99 million kg, or 99,000 tonnes just for the US. Worldwide, by 2020, its estimated that lithium-ion batteries for vehicles will require at most 70,000 tonnes per year, while various mining industry groups claim to be able to ramp to the high figures needed just themselves. This area appears to be well covered.

Finally is cost. Even at $250/kWh (the 2020 industry target price), lithium’s only about 2% of the battery price. The price for LCE is about $8/kg, or about $4.80/kWh, even doubling it doesn’t have a much of an effect on the price – from 2% to 4% of total cost in 2020.

We will still need to figure out what will come after lithium, though some companies are already laying the groundwork for the post-lithium era. But the doomsayers don’t have much of a leg to stand on, and we still haven’t got into harvesting lithium from seawater (at a first-generation technology price of $22-32/kg, with enough lithium for 18 trillion Tesla Roaster battery packs).

A123 Battery Technology – LiFePO4

A123 systems has been a big name in batteries since the plug-in revival started again two years ago. One unique property of the A123 batteries is that instead of prismatic cells (that is, rectangular prism), they’re cylindrical, like the AA batteries that go in your digital camera.

Their chemistry of choice is lithium iron phosphate, or LiFePo4. Their current premier cell that they have specifications available for is the ANR26650M1A, or just M1 cell. This cell packs about 7.6Wh in one cylinder about 6.5cm tall (2.55 inches) and 1.5cm in diameter. That means you’d need 2,100 cells to make a 16kWh battery, and that many cells would provide more than necessary power to supply the electric motor.

One of the rumored reasons why GM chose LG Energy over A123 is that because A123 was unable to produce prismatic cells, and GM needed prismatic cells to fit the necessary 16kWh in the Volt without taking up any more room than they already are. However, this is in direct conflict with Chrysler’s assertion that they are working with A123 on a prismatic cell. The M1 is also the cell that the could be in the Raser Electric Hummer H3, based on a reference to the cell in the H3 promotional video.

A123 is happy to tout their cycle life – their specification sheet has a graph showing that at 45°C (113F, not an unreasonable temperature to keep batteries at during usage) the cycle life exceeds 1000 cycles and maintained just under 90% of its original capacity. At the steady rate of decline showed on the graph, it appears the battery could get up to 1,750 cycles until capacity was 80% of original capacity at 1C charge and 2C discharge.

We’ll see if Chrysler can make it out of Ch 11 and the merger with Fiat to create these electric cars they’ve planed on making, or if A123 gets a better dance partner (Ford?) before the prom is over.

Analyzing Battery Performance Characteristics

There are several metrics to how batteries are measured. And those metrics play various roles in determining how well the batteries would (or wouldn’t) perform in an electric car. From standard hybrids to plug-ins and pure electric vehicles, they all have different battery needs.

We’ll start with the basic measurement of capacity. Your vehicle’s fuel tank might hold 19 gallons of fuel, and the battery equivalent is energy, measured in kilowatt-hours, or kWh. Sometimes the figures are offered in Amp-hours or Ah, to get kWh multiply that figure by the cell’s nominal voltage.

A laptop battery might have around 0.05kWh of energy, while the Chevy Volt has 16kWh, so you can image how many laptop batteries you would need to put in a car to get 16kWh. The biggest battery in a vehicle is the Telsa Roadster’s with 53kWh.

It is estimated that a small sedan would use about 200Wh per mile of driving, and a large SUV would use around 400Wh per mile. Those are average figures, with regenerative braking decreasing city driving figures and highway driving increasing those figures. As the vehicle weight go up, and as your driving speed increases, the amount of energy needed per mile goes up as well. Obviously, increased weight requires a greater force, and aerodynamic resistance increases as the square of speed, so the force required to cut through the air at 70MPH is twice of the force at 50MPH.

So how does all that energy get from the battery to the electric motor? It goes through an inverter to convert the DC (direct current) energy into AC (alternating current) energy to power the motor. This raises the issue of how much power can those batteries deliver at any given moment.

Reading from a battery’s spec sheet, you’ll usually find a pulse power rate. This is measured in W (for each battery) or W/kg, and is the short-term power the battery can put out. Combining this with the total number of cells or total cell weight will determine the maximum power the batteries can deliver to the motor. The motor in the Tesla Roadster is 185kW, and the Volt’s motor is about 110kW.

One of the most important battery characteristics is the energy to weight ratio, usually called energy density, measured in Wh/kg. This is the battery’s usable energy divided by the weight of the battery. This is the most critical factors when it comes to examining batteries – the energy density determines how heavy the battery is, which is a very important factor when it comes to automobiles. Closely correlated to energy density is the energy to volume ratio, measured in Wh/L, this determines how large the batteries are.

Today, automotive lithium ion batteries are approximately 70-100Wh/kg. This means for each kWh of energy storage, the battery weighs around 10kg, or 22lbs, plus other necessary equipment to connect the batteries together, to cool them, protect them in case of an accident, etc. It is hoped that energy density will increase approximately 10% per year for the next 10 years, more than doubling by 2020 and providing for cutting battery size and weight in half.

The next most critical attribute for an automotive battery is the cycle count. This is measured in the number of complete battery cycles until the battery can only hold 80% of its original capacity. A complete battery cycle is when the battery has been discharged and charged at its full capacity. So discharging a battery 50% twice or 33% three times, both equal one complete cycle. Batteries also have an expected calendar life, but this isn’t related to the cycle count.

To extend the the cycle count of the battery, you can use a smaller depth of discharge. The Chevy Volt is the perfect example. It has a 16kWh battery but only will use 8kWh, charging to 85% total capacity and discharging down to 35% for daily driving on electricity. Using only 50% of the battery capacity doubles the number of recharges the battery can withstand until it can only store 80% of original capacity.

The lithium ion battery in your laptop has a life of 18-24 months, and a cycle count of around 300. This isn’t anywhere near suitable for use in electric vehicles, so different battery formulations that last longer and have higher cycle counts are being developed. No one will really know what the Volt’s batteries are capable of until they start selling units, but the battery would need to be capable of around 3,750 recharges (a cycle count of 1,875).

California regulations require electric cars to have batteries that are warrantied for 10 years and 150,000 miles, so automakers are targeting those figures. Granted you have to live in CA or have bought it there to be covered, but because the market is so large automakers really have no choice but to match those warranty numbers.

Finally in this battery tutorial is the charge/discharge, or sometime just called the charge rate, noted as nC where n is an integer (1C, 2C, 6C). This can have an affect on the cycle count – the faster you charge and discharge the battery, the fewer cycles it is capable of. 1C is charging the battery so it will recharge in 1 hour – so an 11Ah battery charged at 11A (at the cell nominal voltage) is being charged at 1C, 22A would be 2C, and 66A would be 6C. Adding up all the cells in a battery pack would tell you what the total current the motor would be capable of receiving.

So thats it as far as this battery tutorial goes.

Sunpower publishes paper on LCOE

I just came across a whitepaper on SunPower’s website that extensively went over the Levelized Cost of Energy and how the drivers of solar power are working to decrease costs, and a glimpse of where we might end up in four years.

The report (PDF) is available and goes through the all of the steps on how to calculate the LCOE and what factors go into designing a large scale solar power system. There are a few places where I disagree with their numbers but overall the report is fairly accurate (their maintenance figures a little low – not too bad, but for us our maintenance cost per kWh is not close to one cent or half a cent as they might claim in some of their cases).

There are a few highlights to point out in this report. First was a reference to a report on panel degradation (source report PDF). They tested 23-year old solar panels and found that they had only degraded 4%. Further, there was nearly no noticed degradation from years 1 through 20, with nearly all the degradation coming in a few year window between years 20 and 22, with the last year of the survey having leveled off the degradation.

Next is that most plants are financed under forecast power production, and that is usually grossly underestimated. This I have also found to be true – our guaranteed output is far less than our actual output – by more than 10%.

The biggest item in the report is the following quote…

In SunPower’s case, the grams of polysilicon consumed to manufacture a watt at the solar cell level declined from 13 g/W in 2004 to 6.3 g/W in 2008 and is planned to decline to an estimated 5 g/W with SunPower’s Gen 3 technology now under development. By 2011 this approximately 60 percent reduction in the use of silicon, coupled with an approximately 50 percent decline in the price of polysilicon, will independently drive large cost reductions for PV panels.

So while panels might have cost $5-6/Wp back in 2004, the increase in cell efficency, reduction of the quantity of bulk silicon used as well as the reduction of the cost of silicon due to the crappy economy and oversupply due to added manufacturing capacity, the cost of a panel could drop down to $2/Wp, and reducing overall costs from $7-8/Wp to $5/Wp and closer to grid parity.

While this is sort of a PR/promotional piece, the numbers in the report are backed up by my real world experiences. As long as the world doesn’t fall apart anytime soon, solar power is on track.

[Edit 6/16: Updated link to Sunpower LCOE paper after their website redesign]


My boss at work turned me on to Coolerado air conditioners. The principle behind the cooler is novel, and seems to not be some vaporware or scheme (they have recieved awards and letters from the US Department of Energy and the Governor of Colorado). While I’ll be skeptical until I see a real unit and can measure things for myself, it does seem like its a real working product. Not only that, but their test system uses “all of the buffalo.”

Coolerado has posted a few YouTube videos (123) talking about their system and how it works. You can watch those or follow along with me.

Their system is broken into two parts – the fan and filter, which draw in outside air and filter it through standard filters you can buy at a hardware store. This will clean the air before it enters the home.

From there, it enters their heat and mass exchanger (HMX). This is where the cooling happens. The incoming air stream is split into channels, with half of the air being used as the “working” air stream which does the cooling work, while the other half is the product air stream (the resultant air that would go into your house).

The HMX is a multiple stage cooling system, where in each stage a fraction of the incoming air is used as the working air stream, and the rest is used as the product air stream that is cold. The working air absorbs water from the wet plate which cools the air by trapping the heat energy in the air in the water (water can hold about 100x as much heat than air can) this cools but also humidifies the air. The wet plate cools as water is evaporated from it, which cools the air on the other side of the plate.

Next, the working air that has already been humidified is used to cool the incoming air by a fraction. By reusing the “waste” air that is humid but still cooler than the warm incoming air, the Coolerado unit seeks to push beyond the “wet bulb temperature”, or the temperature of a wet thermometer bulb in an air mass. Theoretically, the wet bulb temperature is the lowest temperature you can get in an evaporative cooling system. By having a multiple stage process, the wet bulb temperature gets lower with every stage as the working air cools the air left in the system. Their theoretical minimum temperature is the dew point.

Their test system uses that humid waste air, which is still somewhat cool, to cool solar panels which power the fan and solenoid to control the water pump. As someone with extensive solar power experience I can tell you that a 10F degree drop in ambient air temperature can increase your output by 5% given the same atmospheric conditions (solar irradiation, wind, etc).

There are limitations to the system, most notaibly that it is still using evaporative cooling, and it wont be able to cool already humid air. It also requires water – their videos demonstrate a unit for 3,000 sq ft and 20 people uses 4 gallons per hour, or nearly 100 gallons per day, which is about the range a swamp cooler uses for half the size (1,500 sq ft).

There is tremendous upside – the unit uses a fraction of the power of a traditional air conditioner – as little as 10% of the standard energy. Cooling buildings in the dry summers in the southwestern US is a huge energy hog, and if the energy needs could be reduced dramatically it would be a huge relief to energy utilities who would need less transmission capacity and fewer new sources of energy.

I used about 30kWh/day (or about $3.30/day) last summer for cooling (I compared my summer and winter usage and just took the difference – 35kWh/day vs 65kWh/day), so reducing my A/C costs by 90% would result in a 3kWh/day difference between summer and winter, and reduce my monthly energy costs by $90 in the hottest summer months. And due to the lower energy variability on my bill, it would be easier to estimate and cheaper to fit my house with solar power to offset my energy usage.

EVs, Altairnano and Lithium-Titanate batteries

Recently, AltairNano demonstrated their Lithium-Titanate batteries in a real world demo for Indianapolis Light and Power. They had two 1MW/250kWh units, and the batteries and equipment performed very well. The primary use for these large shipping-container sized units is for backing up inconsistent power sources like solar or wind. The units had a 90%+ efficiency returning the stored power to the grid.

But thats not what I’m talking about. Phoenix Motorcars are looking to use these batteries in their electric vehicles. And its these batteries that could change electric vehicles. Well, as soon as they get cheaper.

Lets start with the battery – Altairnano is offering a 35kW pack which would recharge in 10 minutes. However, the problem is that it requires a special off-board charging system. Still, if electric refueling stations had this charging system equipped, you could stop in and refuel and then be on your way in 10 minutes for another 100-120 miles.

Using an on-board charger, it would take approximately 5-6 hours per charge. This would be useful at a mall, or at the office, where you might have a few hours to charge.

This battery technology that does allow for quick charges requires a national standard for recharging capabilities. Having to roll up to a electric refueling station and hope they have a station for your car type is not ideal.

Next is the price – the vehicles they’re being offered in is $50,000-60,000. Compared to a Toyota Camry, the price of gas would have to skyrocket to $6 and even then the car would pay for itself in about 8-9 years.

The plus side is that it could be one of the last cars you buy. The battery will last at least 12 years – possibly longer. The battery would also hold residual value, since the battery is rumored to have up to a 9,000 cycle life – this translates to about 1 million miles! Even at 25,000 per year, thats 40 years. Now whether or not the rest of the battery pack and vehicle can last that long is unknown, but you could still harvest the individual cells and “recycle” the cells into a new battery for much cheaper than making new cells.

Speaking of cost, this is the biggest problem with the lithium-titanate batteries is that they cost around $1/Wh – so a 35kWh battery pack would be about $35,000. Standard lithium-ion batteries are about 50-60% of that price, though they don’t have the 10-minute recharge capability. Of course, its patented so there is only one manufacturer. So that might have an effect too.

Finally, a second smaller issue is the lower weight to energy ratio, meaning your car will have to lug around more weight in batteries (and therefore more batteries to go the same distance, etc) that it would otherwise.

So overall, it looks like a very suitable solution, however they would need to still need some more incremental battery improvements over the next few years to improve the weight situation, and maybe produce a slightly larger pack (50kW) to improve the range slightly (150 mi is really the minimum range to be useful).

The price issue issue can be mitigated somewhat if the battery were to be leased – you’d buy the vehicle sans battery for about $20,000 and pay a certain amount per year for the battery lease for as long as you own the car. This would allow the company to amortize the high cost of the battery over the lifetime of the unit – anywhere between 25 to 40 years. A $50,000 battery pack amortized over 40 years at 5% is $280/mo, or roughly 1,300 mi/mo at $4/gal and 20MPG (includes 12c/kWh power to drive that distance too). Though 1,300 mi/mo is 15,600 mi/yr, so you’ll have to drive a more than the average driver too (but that’s still less than 50 mi/day average).

Like just about every EV technology, the price will need to come down a good deal. But the biggest pros for this battery are the very large cycle count and extemely quick recharge time, and they could win out considering those are two of three biggest questions (range? recharge time? battery replacement?). With a 150 mile range and a 10-15 minute recharge time, it could win over those who are skeptical.

Solar Energy Pt 3

In part 1, I talked about the basic of solar power.

In part 2, I went into detail about thin-film technologies that stand to dramatically bring the price down.

In this part, I’ll talk about Solar Thermal, focusing in on Concentrated Solar Power, or CSP. This is using the heat energy from the sun to generate power.

Before I begin, some housekeeping. I found an article on west Texas wind power interesting because of the information provided as well as the graph that shows how much power is consumed and how it was generated (coal, natural gas, etc). Just about all the power generated for peak demand (between baseload at 35GW to 61GW at peak demand) as well as an additional 15GW 24/7 is all natural gas. Now regardless of which solar mechanism you use (PV, thermal, etc), that is a lot of natural gas and the resultant pollutants that would be removed if solar gets enough traction to replace a large part of the peak demand.

Likewise, oil tycoon T. Boone Pickens is even supporting west Texas wind power. Wind could help abate the usage of natural gas he says, to be used in vehicles as a replacement for gasoline. While I’m not necessarily in favor of that aspect of his plan, it might be a preferable alternative to high gas prices, and made useful in range-extended electric vehicles (REEV – first x miles on electricity, further range on some other fuel).

Also, Ars Technica tries to calm everyone down about supposed shortages of Indium and Gallium (two key components to the production of CIGS thin film solar cells).

On to the issue of solar thermal energy. I’ll start with a very basic way to use heat to reduce the use of power (either electric or natural gas) – rooftop water heaters. By circulating water with a small 1HP pump up to your home’s roof in a black painted tube or bladder, it will heat up. This is a good way to provide for hot water during the day for either your house or your swimming pool (which is common in Las Vegas).

I’ve even seen alternate implementations of this tactic. Back a few years ago on a camping trip in the Utah high desert, folks on the campsite next to us had black bags full of water they left in the sun while they went on a hike. When they came back the water was hot and ready for them to mix with some colder water to take a shower.

OK, so onto solar thermal power generation. There are several types – parabolic trough and power tower are the two most common. After that, there is dish stirling (using a stirling engine as the focal point for an array of mirrors), Fresnel concentrators and reflectors and a recent invention from MIT that can flash boil water for any number of applications.

Lets go over each type, along with an example.

Parabolic trough is where you have mirrors around a tube containing a heat transfer liquid to focus sunlight on the liquid to heat it. There are several of these types of power stations online, including the 64MW Nevada Solar One. I thought I had heard rumors about troubles, but after some googling, I found this PDF that showed some of their production from June 2007, and it was peaking between 55 and 60MW from 10AM until about 4PM, and from there it trailed off until just before 7:30PM. One of the interesting items also noted in that PDF was the future goal of developing and commercializing thermal storage. Doing this, the plant can siphon off power early in the day when the peak demand hasn’t materialized, and then use that energy at the peak (and sell it for more $) as well as after the sun sets until about midnight the peak finally subsides. The trick is to see if they can figure out

Next is power tower – these designs use an array of mirrors on two-axis trackers on the ground, which reflect the sun’s rays onto a tower holding either water or other heat transfer material to ultimately generate power. There is a lot of momentum behind power tower designs – PG&E in California has agreed to buy power from up to 500MW of power tower plants in CA built by BrightSource Energy. There is an optional expansion of 400MW, with the first 100MW scheduled to go online around 2011.

Next is an interesting technology called Linear Fresnel Reflector, or Fresnel Reflectors. This is where the mirrors, either slightly curved or flat, are mounted just above the ground and then rotate along one axis to heat an elevated conveyance filled with water or some other heat transfer fluid. A company called Ausra has just opened a 700MW/yr Linear Fresnel Reflector manufacturing plant in Las Vegas. The manufacturing plant may only employ 50 people, but the resulting construction jobs, as well as the permanent Operations and Maintenance (O&M) jobs for that 700MW/yr will have a large impact.

Dish/Stirling systems are quite unique. A Stirling engine is an engine that generates energy through concentrated heat. Basically, the heat is focused on an area that contains a gas, and when its heated, it expands. That pushes a piston and generates the movement. After the gas has expanded, its allowed to cool through transfer to another piston, and from there it starts all over again. So the application of this is to use of a dish to focus tremendous amounts of energy into the Stirling engine and generate energy that way. Currently, Stirling Energy Systems should be building an array in Southern California called Solar One (not to be confused with the now-shuttered power tower-based Solar One that is also in Southern California), which is expected to eventually grow to 500MW over 4 years, and possibly 850MW. Power production was supposed to start in 2009, however no announcements have been made as to the progress of a 1MW test array or BLM environmental approval. They also were supposed to build a 300MW as well, but no announcements have been made for that either.

Finally, the MIT project is interesting, they purport that the unit cost per dish is very cheap yet it provides steam for whatever purposes – either steam for a building or turning a turbine for electricity generation. Though for the purposes of electricity generation, you’d have to set the dishes up in parallel, which would require more hardware and that can raise the per unit costs dramatically. The students involved have formed a company and are working to productize the dish.

And thats it for solar thermal.

Solar Energy Pt 2

In part 1, I covered the two different types of solar power and the basic on cost and ROI.

This is part 2. I’ll cover some future developments, specifically thin-film technologies which could revolutionize solar power. But TF has its drawbacks too, specifically low power efficiency per sq meter.

This entry I wanted to cover thin-film based technologies. This is a branch of photovoltaic (PV) solar energy.

There are numerous entrants into the thin-film market. I cant cover them all or I’ll be here all day writing.

I’ll start with the one with the biggest brand recognition, mostly due to who is investing in it (Google), and that is Nanosolar. They are producing a type of cell called CIGS (Copper indium gallium selenide). A few weeks ago they posted a video on their blog about their new roll-to-roll printer that would allow them to produce 1GW of solar cells per year. Now granted, that’s not the only piece in the manufacturing pipeline and they didn’t disclose the efficiency of the cells produced from the unit, but the impact is huge if it can really produce that volume of cells. (some back of the envelope math says that if they run that unit 8 hrs/day, 7 days a week, 52 wks/yr, the solar cells that are made will be 12% efficient, for them to produce cells less than 8% efficient would be a waste because it wouldn’t be cost effective in terms of installation)

The most amazing thing is the cost – Nanosolar claims that tool only cost them $1.65M. At $1/Watt, the unit is printing revenue of $1B/yr. Even at 1c/Watt (an unheard of price for solar power, considering the going rate today is 400x that amount) the unit would still be printing $10M/yr in revenue (6x capex). Beyond that, they state that there is the possibility that they could run the tool faster – up to 2,000ft/minute from the current 100ft/minute. This would result in 20GW of solar cells per year from the single tool. To place that in a useful context, 20GW of solar panels installed on rooftops in California could accommodate 75% of the difference between baseload and peak power demand on the sunniest, hottest days of the year. It would certainly be the end of rolling blackouts.

Next up is First Solar. They are producing a type of thin film cell using CdTe (cadmium-telluride). They are further along than Nanosolar, since they are producing panels and implementing projects like a 40MW utility scale project in Germany. And their cost is cheap too – about 3.25Eur/Watt installed ($5/W at today’s exchange rates, stupid weak dollar), compared to the standard cost of $7/Watt. The problem is land – the efficiency of thin film cells is lower and the installation is using 75W panels for a total of 550,000 panels and roughly 300 acres. So while the price looks great, putting 18 panels on your roof will only generate 1.3kW of energy, or 13 100W light bulbs. More efficient panels are needed for smaller installations.

Another CIGS producer is Global Solar in Arizona. They recently expanded their factory in AZ and opened a factory in Germany.

Not everything is peaches and cream however. A few thin film companies have had to delay, scale back or retool their production plans. Miasole had to retool their commercial production line after seeing low efficiencies, even though their research and development production line saw the 8-10% target they were hoping for.

As I mentioned at the beginning of part 1, the problem isn’t the research of the technology. Its the mass production milestone. To go from 1MW to 10MW to 100MW and 1000MW in annual production capacity over the next five years to provide the energy we need.

Even with the 10% efficiency targeted, panels currently in production are only rated at 75W versus 224W silicon PV panels that are available today. The lower rating or the panel increases the amount of land needed and makes rooftop installations less cost effective due to the lack of space and limited amount of panels that can be installed. A 1500 sq ft ranch home might be able to put 20 200W panels on their roof for a 4kW installation, but at 75W the output would only be 1.5kW. Due to the way the economics work with small installations, the payback time could be much longer because of the increased $/Watt cost as well as a decreased power output (only 30% cheaper for providing a smaller part of your electric consumption).

The sweet spot for rooftop installations is about 3kW-5kW, this provides enough power to be worthwhile and still be around only 20-25 panels, so we’ll need to get thin film panels up around 135-150W. I’m confident we’ll get there, but it might take a few years. In the mean time, the panels will be targeted towards utility scale projects.

With solar power there are three key aspects: price, efficiency, and quantity available. Right now we have efficiency in the bulk PV market, and in the thin film we will soon have price and quantity, with questionable efficiency.