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To make optimal use of solar powered equipment and appliances, it is essential to understand the mathematics behind how they work, which is why The Solar Refrigerator Company has published this guide
The Solar Refrigerator Company is paving the way in the industry with the launch of the new highly efficient Dometic DMC4101 10 cu ft RV Refrigerator. Alongside this solar refrigerator launch, the company is also publishing a guide on how to calculate the requirements needed to power solar appliances. With the guide, it is now easy for customers to accurately determine the number of solar panels and solar batteries required to properly operate a solar refrigerator, solar freezer, or the newly launched Dometic DMC4101 10 cu ft RV Refrigerator anywhere in the world.
In order to determine what is needed to power a solar appliance, it is quintessential to know the average solar hours or peak sun hours of the city or country, where the appliance will be used.
For customers in the United States and Canada, information about peak sun hours can be obtained via http://pvwatts.nrel.gov/. At the top left corner of the website’s homepage, next to “Get Started,” users will find a text field. Here, Americans are expected to enter their zip codes while Canadians should enter their postal codes and click GO.
When the page loads, users need to click on “RESULTS,” which will take them to a table of results from January to December. They will see a column showing “Solar Radiation,” which contains the average monthly solar hours for an address spanning the 12 months of the year. If a user plans to run their appliance all year round, they should note the smallest figure of the year. For customers with cabins, for example, that are only used seasonally, record the smallest value in the months of use of the appliance. The number selected will be used as the Average Monthly Solar Hours to be used in the calculations to follow.
People living outside of the US and Canada can discover their location’s sun peak hours by visiting http://solarelectricityhandbook.com/solar-irradiance.html. Customers are expected to select the country and town or city closest to the area where the appliance will be installed on the webpage. Next, they need to choose the direction in which they plan to install the solar panel. If they do not know that information, they use the ‘Facing directly North’ or ‘Facing directly South’ estimates in the third field.
The website will present the Average Solar Insolation Figures for each month of the year. Users need to record a figure that is the smallest figure of the year, and the number recorded will be used as the Average Monthly Solar Hours to be used in the calculations to follow.
After using either of the above websites to determine the Average Monthly Solar Hours, users can proceed to perform the calculations. Calculations for solar refrigerators and solar freezers can be conducted as follows:
Power Consumption x 1000
________________________ = Solar Panel Size (in Watts)
Peak Sun Hours
Most of the product pages on Solar Refrigerator Company’s website show the Power Consumption of each model. The Dometic DMC4101 10 cu ft RV Refrigerator has a power consumption of 0.9 kWh/day; for the SUNSTAR ST-16RF it is 0.6 kWh/day and the SRC450DW it's 0.72 kWh/day. We will use US zip code 90210 as the location in this evaluation. This location using the pvwatts.nrel.gov site has a peak sun hours of 4.14.
So for the DOMETIC RV FRIDGE:
0.9 x 1000
_________ = 217.4 watts of panels (excludes 25% solar panel inefficiency)
Finally, multiply 217.4 by 1.25 = 271.8 watts of solar panels, which accounts for inefficiency of 25%. This is the minimum solar panels needed to power this solar refrigerator.
To determine the batteries needed to run this appliance, the key figure is the power consumption, which in the case of the Dometic refrigerator is 0.60 kWh/day. The best practice to maintain the longest service life of a solar battery is to avoid discharging more than 50 percent of its capacity.
Hence, calculating for solar batteries for the Dometic RV Refrigerator:
0.90 kWh/day x 1000 = 900Wh per day
900 x 2 = 1800Wh per day. The multiplication by 2 is because 50% of the battery capacity is half 100%. So, the battery capacity requirement is at least 1800Wh. A 12-volt 100Ah battery has a capacity of 12 volts multiplied by 100Ah = 1200Wh.
Thus, 1800Wh/1200Wh = 1.5 12 volts 100Ah batteries. These calculations can be applied to determine the required solar panels and batteries needed to power anything in a home or business.