[MLB-WIRELESS] Solar power modelling

[Kym Michael]

I worked out from some previous posts that about 40 Amp hrs storage were 
required.

I have been buying some ex one-tel backup batteries for another purpose.

45 amp hr 12 volt gell cells, new unused backup replacements. Obviously 
stored longer than desirable but still holding about 12.75 volt.

I paid about $65, he had pallets of them.

I others interest I can follow up to see if I can get more



At 12:39 AM 4/3/2003 +0100, you wrote:
>Hi,
>
>A week or so ago I asked a question about solar powering nodes and where to
>get good data and simulation information. I got little response and several
>I want to know as well messages. Here is what I found over the last week:
>
>Solar data.
>I was looking for good sources of solar radiation data.
>http://www.squ1.com
>A consultancy firm that appears to be part of Cardiff University in the UK.
>They do tools and consultancy on building design. In there shareware section
>they have a program called the weather tool. They also have available for
>free download hourly data files of weather for lots of locations around the
>globe. The unregistered version of the weather tool does not allow you to
>export weather data to a text file. it is however a very useful and
>instructive program.
>
>Meteonorm
>http://www.meteotest.ch/en/mn_home?w=ber
>Meteonorm is just the ticket. You can download an evaluation version from
>their site. They have an extensive database of weather for the whole globe
>on an hourly basis. The download version only has 1 years data in it will
>only allow you to export data to a text file for a limited number of cities,
>Frankfurt, Tokyo, Accra (Ghana), Brazillia and somehwere else I forget. What
>makes this program ideal for our purpose is that you can define an arbitary
>inclined plane and get it to export the incident solar radiation levels hour
>by hour for a whole year. Most excellent.
>
>The model
> >From the meteonorm package I exported a data file for Frankfurt and Accra
>(Ghana) for an inclined plane facing north at and angle of 45 deg (not
>otimum angle).
>The output looks like this:
>
>1       1       7       7       51      46      91      67      74      27.3
>1       1       8       8       248     122     365     151     424     27.9
>1       1       9       9       393     215     470     235     352     29.4
>1       1       10      10      606     236     712     275     545     31.3
>1       1       11      11      768     257     879     307     637     32.7
>1       1       12      12      764     359     844     401     466     35.1
>1       1       13      13      801     339     887     383     528     37.4
>1       1       14      14      677     372     733     394     372     38.6
>1       1       15      15      533     342     584     361     272     39.3
>1       1       16      16      287     247     287     237     73      39.0
>
>
>
>We are interested in column 7 which is the radiation incident on the
>inclined plane. The help documentation for meteonorm tells you what all the
>columns are.
>
>I imported this into excel and added a few formula.
>
>The model is very simplistic. It models the charge in a battery that
>receives input from the solar cell and supplies output to the access point.
>For each hour the battery stores a net input of solar radiation*area of
>cell*cell efficiency*batt efficiency
>and has an output of access point power. Units in Wh
>
>Solar radiation in W/m2
>Cell area in m2
>Cell efficiency is proportion of incident ration converted to electicity,
>number in range 0-1
>Batt efficiency is proportion of input power stored in battery, number range
>0-1
>
>battery charge is in units of Wh
>
>The equations for calculating the charge in the battery are clamped at 0 and
>the battery capacity in units of Wh
>
>The spreadsheets for Frankfurt and Accra are at:
>http://www.sentinet.demon.co.uk/wireless/frankfurtmodel.xls
>
>http://www.sentinet.demon.co.uk/wireless/accramodel.xls
>
>They use the following assumptions:
>Solar cell efficiency 20%
>Battery efficiency 66%
>
>The solar cell efficiency of 20% may be way off and perhaps a value of 0.1
>might be more realistic.
>
>Conclusion:
>It is surprising how big a battery you need and how small a solar pannel. If
>we take the model for Accra in Ghana which is a lot sunnier than Frankfurt
>then you need a battery reserve of about 5 days worth of power but a solar
>pannel of only 0.1 square m.
>Frankfurt needs a pannel of 0.2 square m and a battery capacity of 7 days.
>
>A longer run of solar data is needed for a good analysis but this requires
>buying a copy of meteonorm which is $390US. It comes with 10 years of
>weather data. A more complex model would be good.
>
>Anyone know anyone with a registered copy of this program ?
>
>Lyndon
>
>
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Best Regards, Kym Michael


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