Jianguo Xu’s Recent Comments

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  All we need is a long cycle life battery

  Gar, You quote of electric vehicles need 200 miles or range is probably right but irrelevent. I for one expect PHEV to come into being first. We are talking about 20-60 miles of electric range. Say for the sake of discussion, 60 miles of range for the PHEV of our discussion. You are right that the current NiMH battery cannot last tens of thousands of cycles. But what if someone can extend that life to what is needed. What if I tell you that I know someone who I believe has a way of doing it, and that such a battery is going to be cheaper than NiMH battery, at least no more expensive?

  Assume at mass production the battery cost can be $400/kWH (mass production cost of $250/kWH has been quoted by EPRI for NiMH batteries for EV applications), and we need 20 kWH of capacity. This gives a battery cost of $8,000 per car. At $3/gal fuel cost, this is competitive. Plus, if you use the vehicle for V2G applications, you will have give some credit to the vehicles.

  My point is we are not far - all we need is to make the battery long lasting enough. And that may be within our grasp. All what it takes is time and money for the development of the technology.

  My understanding is this is a forum for alternative energy solutions. Most of what we are talking about are not yet economical. Therefore, R & D money is needed in areas that are promising. We need to identify them. Besides, the current pricing structure does not price in the environmenal impact of eneryg use. If in future  pricing of energy will correctly reflect the true life time cost that includes the environmental and health impact of fuel use, then we will see the economic numbers for these alternative energy solutions much better looking. On It's not the key to making renewables work posted 2 years, 11 months ago 23 Responses

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  need for long life batteries

  Gar, you are right in pointing out the need for long cycle life batteries. Excellent point.

  Your conclusion, however, is based on the current NiMH battery. Progresses are being made in this direction. As Scatter pointed out, Altainano disclosed that their batteries can last over 15,000 cycles. I am not going to judge Altairnano's credibility. Nor am I going to say that their battery is good enough for PHEV applications. My point is: your point is a very good one on the need for a long cycle life battery. However, we cannot judge future based on the current technology, assuming we will not make the necessary progress.On It's not the key to making renewables work posted 2 years, 11 months ago 23 Responses

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  Solar thermal for heating and cooling

  While electricity generation from concentrated solar thermal or multijunction PV may play an important role in the future, another important area that is already commercial is solar thermal heating, especially for heating water.

  Here is why it makes sense: assume concentrated solar thermal or PV has a net efficiency of 33.3%, including the transmission losses (we are not there yet, but may be close). Assume for heating or cooling in buildings and homes, we have a coefficiency of performance (COP) of 3. We get a "round trip" efficiency of 1. More importantly, the capital cost is very high.

  The current simple solar water heaters of course do not have an efficiency of greater than 100%. However, if a thermally activated heat pump with an COP of, say, 2.0 for space heating and 1.3 for air conditioning, is used, then the overall COP can be greater than 1, beating the more expensive version.

  Of course, there are other sources of energy we should use in solving space heating/air conditioning energy source issue. Geothermal simply stands out among them. Combining geothermal energy with solar thermal heat pump is a great way of greatly reducing energy consumption in HVAC area. My understanding is that space heating and cooling consumes close to 1/3 of the total energy  consumption of the society. Therefore, we are not talking about a small issue - it is almost as important as that of transportation.On It's cheaper than photovoltaic posted 2 years, 11 months ago 34 Responses

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  PHEV and EV for storing electricity

  When plug-in HEV with 60 miles of electric range and electric vehicles become widespread, at least a significant portion of the capacities of their batteries can be used for storing electricity produced from solar (and wind) energy, and/or used as the means for load leveling of the electrical grid. You are talking about up to 20 kWh of storage by cars alone for each car when all the vehicles have 60 miles of EV range. If there will be 100 million PHEV/EV in this country, the storage capacity can be as high as 20 x 100 = 2 billion kWh/day.

  For wind energy storage, the battery may be able to charge and discharge a few times a day as a means of load leveling.

  I guess 2 billion kWh/day is likely enough to make up the shortage in nights in this country - remember we will always be able to generate a significant portion of the electricity during nights from wind, hydropower, nuclear, and other types of power plants.

  The key is to develop rechargeable batteries with very long cycle life and a reasonable cost, I believe. On Efficiency is the key posted 2 years, 11 months ago 31 Responses

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  Multijunction PV - solar concentrator

  Multijunction PV can reach efficiencies of over 30%. As a matter of fact, some of them already approach 40%. It is likely that 50-60% can be reached sometime in future. These devices can be used in conjunction with solar concentrators which can greatly reduce the cost of the PV cells. The PV cells are typically 1 cm x 1 cm in size. Therefore, the concentrator can be 30 cm x 30 cm each for a 900 sun concentrator. This makes the concentrators much simpler to build than those used in solar thermal plants.

  Currently Boeing and Emcore are the leading companies in producing multijunction PV's.On It's cheaper than photovoltaic posted 2 years, 11 months ago 34 Responses