Posts Tagged ‘active solar water heating systems’

8 August

Dr. Christopher Case (of Oxford PV) Discusses Game-Changing Future Transformer of Solar Power Generation-Perovskite Based Solar Cell Technology


Dear Friends, Visitors/Viewers/Readers,

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I  saved the most potential game-changing solar technology in the last interview spot, the update of Perovskite-based solar cell technology with the Chief Technology Officer of Oxford PV, Dr. Christopher Case, of this series of Intersolar North America 2015 interviews. Recalling one of our earlier posts, I wrote about Perovskite, a calcium titanium oxide mineral discovered in the Ural Mountains of Russia in 1839. This new old material is generating quite an explosive buzz because scientists have found, in recent years, that it is a great material to be used in solar absorption applications. It can be made simply and inexpensively by using common wet chemistry lab methods and low cost equipments instead of the expensive deposition equipments common in the semiconductor industry. To take a look at how this process is made cheap and accessible, I’m sharing the video below:

These solar (photovoltaic) cells are made in tandem (layer by layer) fashion on a specially coated glass support. In the video above:

  1. the glass is coated with a dense layer of titanium dioxide, by robotic arm, to prevent electrical charge generated by sunlight from leaking out of the cell.
  2. a less dense porous oxide layer covers the dense oxide layer (usually titanium dioxide, other oxides may also be used).
  3. a simple high speed spin coater deposits this layer from solution and spreads this coating evenly across the device.
  4. heating this glass/device in an oven conditions it for solar cell use.
  5. prepare the Perovskite material (which absorbs in the broad range of solar spectrum) by combining 2 precursor materials:   PbI2 (lead iodide) & CH6IN (methylammonium iodide)
  6. drip the liquid phase mixture (from 5.) onto the oxide coated device (from 4.)
  7.  spin the resulting device in 6 to assure even coating
  8.  applying halide solution
  9.  heating the device resulting from 8 on a hot plate–>spontaneously crystallizes precursors in freshly deposited liquid
  10.  color changes also result from crystallization process resulting from 9.

Such tandem product has the advantage of being able to be introduced into existing infrastructure of current silicon module manufacturing process, boosting its efficiency. With added few steps toward the end of the production line, the coating (equivalent to second solar cell) takes advantage of the blue portion of the solar spectrum and may improve the solar cell efficiency by 20-25% above the underlying silicon. The fact that Perovskite-based solar cell technology is of earth abundant material also insures its availability and low cost. Its high absorption in solar spectrum enables it to have comparable characteristics to that of gallium arsenide. Its ability to change its sensitivity to different band gaps in solar spectrum allows it to make different architectures in tandem solar cells. It can truly be considered as the Custom Solar Absorber! In short term,  Perovskite-based solar cell may boost the efficiency level of existing technology and in the long term, it may be a stand-alone technology with closer efficiency level to that of gallium arsenide but at a much lower cost. It may potentially be sprayed, ink-jet printed, dip-coated, etc. It is no wonder that Dr. Case commented, “the perovskite in solar application is the fastest increasing photovoltaic efficiency of any solar photovoltaic thin film material ever! In just a few years, it went from a lab efficiency of about 6% to well over 17%…the material is a very good solar absorber….bringing the material to 25% efficiency in a monolithic layer and 30%+ in a perovskite tandem layer….potentially the future replacement for silicon.”

The perovskite thin-film solar cells, is currently being developed by Oxford PV (a spin-out from the University of Oxford in 2009-2010 to commercialize this technology, which has exclusively licensed the intellectual property developed by Professor Henry Snaith and his team of 20 scientists). Below, Professor Henry Snaith will embellish upon the development of this solar technology:

Oxford PV plans on continuing to optimize this technology’s cell efficiency and accelerate the transfer of the technology into production. Furthermore, it aims to develop the range of substrates to which the cells can be applied. With its promising future, we, the solar enthusiasts and investors alike, should keep our eyes on Oxford PV in the coming years. In the next few years, we anticipate that Dr. Henry Snaith and his team of scientists will continue to tackle challenges in trap densities, doping densities, mobility, mechanisms for free carrier generations, etc., to further improve device performance. You will find that many in the solar industry share the optimism of Professor Henry Snaith and Dr. Christopher Case.

For those of you interested in more details about Perovskite-based solar cell technology, please refer to the two videos below:

1. Introducing Perovskite Solar Cells to Undergraduates:

2. Perovskite Solar Cells: From Device Fabrication to Device Degradation-Timothy Kelly:

~have a bright and sunny day~
Gathered, written, edited, and posted by sunisthefuture-Susan Sun Nunamaker

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4 January

Swedish Prime Minister Fredrik Reinfeldt Believes in Sun Is The Future !


Dear Readers,

If you are in favor of renewable,  clean, or solar energy, please sign this petition for FIT/CLEAN Program, accessible at Thank you very much.

Greetings, my friends and readers,

It is a pleasant surprise for me to find out that Swedish Prime Minister Fredrik Reinfeldt

Swedish Prime Minister Fredrik Reinfeldt (from Wikipedia)

also believes in Sun Is The Future !

On November 30, 2009, Fredrik Reinfeldt, the 32 nd Swedish prime minister which holds the rotating EU presidency met with Huang Ming, the vice chairman of ISES (International Solar Energy Society) during the China-EU summit held in Nanjing.  Prime minister Reinfeldt made a trip to Himin 3G solar water heater outlet which stocks the new third generation water heaters.  While some may have thought that China plays a passive role in environmental protection and carbon emission reduction, Reinfeldt told Huang Ming that the China Solar Valley had been applauded roundly by European media, improving China’s image in the world.  Before leaving, Reinfeldt inscribed the words “Sun is the Future” on the sign board of Utopia Gardens–a solar residential community developed by Himin.  The Swedish Prime Minister also expressed his wish to visit China’s Solar Valley.



China’s Solar Valley:  This is a $740 million project, locating near the northern city of Dezhou, Shandong province, intended to demonstrate how China can both promote and profit from cleantech. It had attracted more than 100 companies and inspired the construction of factories, a research center, and wide boulevards illuminated by solar-powered lights (installation cost of $10 million for these solar lighting along roadways). Dezhou has positioned itself as a hub for greentech, calling itself China Solar City.  Goldman Sachs had invested $100 million in local power Himin Solar Energy Group, the world’s largest supplier/manufacturer of solar water heaters.  China is aiming to have 15% (it is around 9% now) of its power from renewable energy sources (including hydroelectric dams) by 2020.  At present, China’s  increasing coal consumption offsetting gains is a challenge.

Your comments, suggestions, opinions are always welcomed.

written and posted by sunisthefuture-Susan Sun Nunamaker,

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6 April

Solar Water Heater-How It Works (2)


If you are in favor of renewable/CLEAN energy, please sign the petition page showing support for FIT/CLEAN Program at Thank you.

Remember that we are discussing this topic, Solar Water Heater-How It Works, in honor of Ed Begley Jr.. The use of solar water heaters to heat water had a long history in countries/regions where sunlight is readily available.  As a matter of fact, in US, the first solar water heater dates back to 1890s.  By 1920, tens of thousands of solar water heaters were sold in US. However, the use of solar water heaters dwindled once the cheaper fossil fuels became available.  Yes, that was a different time in history and solar water heaters have again made a comeback in US and elsewhere  now that the cost of fossil fuel has gone up. Let’s look at some data/pie chart from 2007 at right   (click on the pie chart would give you a higher resolution view).

new solar hot water installations during 2007

There are mainly two types of solar water heaters:

  1. Active solar water heating systems: where pumps enable the flow of water through the solar water heating systems.
  2. Passive solar water heating systems: where most of the circulation of water occurs naturally, therefore no pump is use

(A) Passive CHS (Convection Heat Storage/thermosiphon)system with tank above collector. (B) Active system with pump and controller driven by a photovoltaic panel

Active systems can tolerate higher water temperatures than in equivalent passive systems, but active systems are often more efficient, more complex, more expensive, and more difficult to install than passive systems and rely on either mains or PV sourced electricity to run the pump and controller.

Since no body ever remembers a long winded speech (as Dale Carnegie once commented)….so let’s keep this one short also.

More of the solar water heater will be discussed in my next post. Stay tuned in at the same bat channel,

Until then, I bid you well~

sunisthefuture-Susan Sun Nunamaker


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