Posts Tagged ‘Sunshine’

7 April

Solar Water Heater-How It Works (3)

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If you are in favor of renewable/CLEAN energy, please sign the petition page showing support for FIT/CLEAN Program at http://sunisthefuture.net/?page_id=1065 Thank you.

Dear friends and readers, let’s continue to look into the workings of Solar Water Heater.  The simplest approach to heat water with solar energy is to simply mount a metal tank filled with water in a sunny place.  The heat from the sun would then heat the metal tank and the water inside and this is how the very first Solar Water Heating systems worked more than a century ago.  But the inefficiency in this system is: once the tank and water has started to be heated, the heat gained would be lost back into the environment until the water in the tank would assume the ambient (surrounding environment) temperature.  Therefore, the challenge is to limit the heat loss from the tank and delaying the time until thermal equilibrium is reached. To meet this challenge, there are three types of solar collectors most commonly used in the solar water heating systems, described below:

An ICS (Integrated Collector Storage) system or batch collector

  1. ICS (Integrated Collector-Storage) systems or batch collectors:to limit the heat loss from the tank back into the environment, water tank is encased in a glass-topped box that allows heat from the sun to reach the water tank, while the other walls of the box are thermally insulated, reducing convection as well as radiation to the environment.  Furthermore, the box can also have a reflective surface on the inside. This reflects heat lost from the tank back towards the tank. (think of an ICS solar water heater as a water tank that has been enclosed in a type of “oven” that retains heat from the sun as well as heat of the water in the tank.  Variations of this basic design may be composed of several smaller water containers and even including evacuated glass tube technology.  Since the amount of heat that a tank can absorb from the sun is largely dependent on the surface of the tank directly exposed to the sun, it follows that a small surface would limit the degree to which the water can be heated by the sun.  Therefore most modern collectors attempt to increase the efficiency warming of the water in the tank by increasing the surface-to-volume ratioThe ICS systems are often installed in areas where the temperature is very low and heating from solar energy is not sufficient. So cold water is first heated in the solar collector, then to the insulated tank, and finally passed to the conventional water heater that ensures the heating of the water to required temperature levels.

    Flat Plate Collectors for Solar Water Heating System (Source: Wikimedia Commons)

  2. Flat plate collectors: these collectors are flat in shape and oriented towards the sun, enclosing a network of piping, applying the basic idea of “oven”-like box.  Here a  pipe is connected to the water tank and the water is circulated through this pipe and back into the tank.  The water tank is now outside the collector that only contains the pipes.  Most of these flat plate collectors’ pipes have diameters less than 1 cm in order to increase the surface-to-volume ratio (recall this would help to increase the efficiency of the warming process of the water).  At the top there is one or more layers of glass or plastic cover on which the sunlight falls. The light is then absorbed by the absorber plate (metal plate such as aluminum). There are piping of water absorbing the heat from the absorber plate.  The most commonly used solar water heating system is the flat plate collectors, which are usually insulated and weather shielded.
     
  3. Evacuated tube collectors: these collectors are comprised of parallel rows of the glass tubes which are exposed directly to the sunlight.  The water piping in an evacuated tube collector is surrounded by two concentric tubes of glass with a vacuum  in between that admits heat from the sun (to heat the pipe) but also limits the heat loss back to the environment.  The inner tube is coated with a thermal absorbent. These solar collectors are usually used for commercial applications where maximum amount of heat to be absorbed and the losses due to radiations have to be reduced.

    Evacuated Tube Collectors (Source: Wikimedia Commons)

    Flat plate collectors are generally more efficient than evacuated tube collectors in full sunshine conditions, but energy output of flat plate collectors drops off rapidly in cloudy or cool conditions compared to the output of evacuated tube collectors that decreases less rapidly.

     

For better understanding of these systems, please stay tuned in my next episode of Solar Water Heater-How It Works (4).  There will be a rather enlightening clip waiting for you.

posted by sunisthefuture-Susan Sun Nunamaker, sunisthefuture@gmail.com
Homepage: http://sunisthefuture.net http://sunisthefuture.com http://sunisthefuture.org

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28 March

Sunshine For All of Us-Insolation

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Dear friends and readers, here is the continuation from March 20, 2011 post on “There Is Plenty of Sunshine For All of Us”:

I  found a wonderful site that has explained the concept of  insolation with more graphical presentatioins: http://www.scribd.com/doc/2410121/Insolation .  Various parts of the world or planet earth may also be seen through this collection of World Insolation Maps, available via: http://www.google.com/images?hl=en&client=firefox-a&rls=org.mozilla:en-US:official&channel=s&biw=1420&bih=1000&q=world+insolation+maps&bav=on.2,or.r_gc.r_pw.&um=1&ie=UTF-8&source=univ&sa=X&ei=eLSFTZXBKu2C0QGOnvHOCA&ved=0CCUQsAQ.
To get a general idea of how much solar radiation there is available in USA, I’d like to share with you some data collected by U.S. Government of Scientific and Technical Information (OSTI) for different states, made available at this site, http://rredc.nrel.gov/solar/pubs/redbook/ So, let’s take a look at some data together:  Firstly, if you’d click on the sunshine state of Florida (specifically Daytona Beach, FL), solar radiation for flat-plate collectors facing South at 0 degree tilt,  during the month of January, produces at minimum 2.7  kWh/m2/day, at maximum 3.7 kWh/m2/day (which average to 3.1 kWh/m2/day).   kWh/m2/day, kilowatt-hour per meter squared per day, is the unit of measurement for energy, in this case, for solar radiation.  Under similar circumstance in Chicago, IL (by clicking on Illinois), the measurement at minimum was 1.5 , at maximum was 2.1 and averaged to 1.8 in the month of January while in Alpena, MI, measurement at minimum was 1.4, at maximum 1.8, and averaged to 1.6 kWh/m2/day. To get an overview of how much solar radiation/sunshine there may be available for the month of January in USA, please take a look at the map below.  Definitely, there will be monthly and seasonal variations.

January PV Solar Radiation (Flat Plate, Facing South, Latitude Tilt) of USA

To determine how much, on the average, solar radiation may be available annually, we simply multiply the amount of   solar radiation or energy is available daily by 365. For  an example of a quick overview of the average annual solar radiation  data (for USA) produced by NREL (National Renewable Energy Laboratory) , take a look at this map located at this site:  Annual PV Solar Radiation (Flat Plate, Facing South, Latitude Tilt)http://en.wikipedia.org/wiki/File:Us_pv_annual_may2004.jpg .

Annual PV Solar Radiation (Flat Plate, Facing South, Latitude Tilt) of USA

Insolation is a measure of solar radiation energy received on a given surface area in a given time.  In the case of photovoltaics it is commonly measured as kilowatt hours per year per kilowatt peak rating.  In case any of you is wondering, peak rating is the amount of energy produced at the moment or instant when highest amount of solar radiation is produced at specifically given conditions.  Recall  my previous post (of March 20, 2011) regarding single or 1- axis vs. dual or 2-axis tracking  device, these trackers are great for optimizing the amount of energy produced for current pricing structure of the solar modules/panels/plates;dual or 2-axis tracker yields about 40% more power than fixed/flat plate (source:  http://www.renewableenergyworld.com/rea/news/article/2010/11/dual-axis-tracking-generates-more-power ) while single or 1-axis tracker yields about 20-30% more power than fixed/flat plate (source: http://us.sunpowercorp.com/power-plant/products-services/trackers/ .  But as the cost of solar modules/plates continue to drop,  the desirability of these tracking devices may also diminish for the fact that there is added initial costs and movable parts (translating to higher maintenance cost).  If solar modules/plates are cheap enough, it may eventually be more economically feasible to simply add more solar modules/plates rather than adding tracking devices. Please keep in mind that the economic feasibility will continue to change as the cost of solar module/panel/plate decreases and price of oil increases.

My friends in USA and  throughout planet earth, we really do have plenty of sunshine, waiting to be tapped.  So let’s try to put it to use.  It is true that at different parts of the world, there may be different  level of availability.  I guarantee that the cost of using solar energy/technology will continue to drop.  The sooner that more of us start to use solar energy, the faster the cost will drop.  More discussions on economic feasibility and various contributing factors will be disclosed in my future posts.  I hope you will have a sunny day, wherever you may be….

 

Posted by sunisthefuture-Susan Sun Nunamaker, sunisthefuture@gmail.com
Homepage: http://sunisthefuture.net http://sunisthefuture.com http://sunisthefuture.org
Any comments and suggestions are welcomed at sunisthefuture@gmail.com

Please also get into the habit of checking at these sites below for more on solar energy topics:

www.sunisthefuture.net

www.youtube.com/user/sunisthefuture

www.kiva.org/team/sunisthefuture

www.facebook.com/sunisthefuture

www.pinterest.com/sunisthefuture

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20 March

There Is Plenty of Sunshine For All of Us!

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If you are in favor of renewable/CLEAN energy, please sign the petition page showing support for FIT/CLEAN Program at http://sunisthefuture.net/?page_id=1065 Thank you.

My concerned friends/readers from Midwest (MI and IL) and Canada, I can assure you that there will be plenty of sunshine for you to also become involved with solar energy projects!  The sunlight that our solar system is exposed to could either be direct (unobstructed by clouds) or diffused (filtered either by clouds or atmosphere).  Although the amount  of diffused sunlight (caused by cloud) would increase as we head northward, solar technology can use either form (direct or diffused) of sunlight to produce electricity by using a well-designed PV (photovoltaic) system.  As a matter of fact, besides geographical location, seasons, elevation, and angle of the sun can also affect the usable amount of solar energy.  To increase the amount of energy produced, solar tracker (either 1-axis/single axis or 2-axis/dual axis) devices are introduced to orient various payloads (such as PV panels, reflectors, collectors, lenses, etc.) toward the sun.  Typically, a 1-axis or single axis tracker has one degree of freedom and changes its orientation throughout the day, while a 2-axis or dual axis  tracker have two degrees of freedom that would change its orientation throughout the day and from season to season.

Azimuth-Altitude Dual Axis Tracker – 2 axis solar tracker, Toledo, Spain

A backyard installation of passive single–axis trackers, DC rated at 2340 watts. Seen here in winter midday position, tilted toward the south. The tall poles allow walk-under and use of the ground space underneath the panels for plantings that thrive on protection from the intense midday summer sun at this location

 

 

 

 

 

 

 

 

 

 

 

At this point, I want to share with you a really cool looking house, the Gemini House/Gemini Haus, that rotates in its entirety and the solar panels rotate independently, allowing control of the natural heating from the sun.  What a great way to ensure that the sun always shine on your photovoltaic array!  Gemini House (or Gemini Haus) was designed by Roland Mosl, to combine innovative solar technology and an eye-catching aesthetic.  It was the first energy plus house (self-sufficient, and sometimes more) in Austria.

Gemini House/Gemini Haus rotates in its entirety and the solar panels rotate                     independently, allowing control of the natural heating from the sun. The inventor stands in the middle of the group

Homepage: http://sunisthefuture.net http://sunisthefuture.com http://sunisthefuture.org
Any comments and suggestions are welcomed at sunisthefuture@gmail.com

Please also get into the habit of checking at these sites below for more on solar energy topics:

www.sunisthefuture.net

www.youtube.com/user/sunisthefuture

www.kiva.org/team/sunisthefuture

www.facebook.com/sunisthefuture

www.pinterest.com/sunisthefuture

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Google+

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