tag:blogger.com,1999:blog-54123251438237694492024-03-13T08:50:28.232+05:30Mixed bagMy notes on whatever interests meSumanth Kavurihttp://www.blogger.com/profile/11033407265529189813noreply@blogger.comBlogger2125tag:blogger.com,1999:blog-5412325143823769449.post-88389942540207152422012-11-01T23:02:00.000+05:302012-11-01T23:03:56.998+05:30Solar power for homes: Some calculations<div dir="ltr" style="text-align: left;" trbidi="on">
<span style="font-family: Verdana, sans-serif;">In my <a href="http://sumanthkvck.blogspot.in/2012/10/solar-power-for-homes.html">previous post</a>, I considered three options for using solar power at home and concluded that an off-grid system is too expensive. Well, why is it expensive? On what basis did I say that? </span><br />
<span style="font-family: Verdana, sans-serif;"><br /></span>
<span style="font-family: Verdana, sans-serif;"><b>How much does it cost to replace a grid connection with off-grid solar power?</b></span><br />
<span style="font-family: Verdana, sans-serif;">I will take the following example</span><br />
<ul style="text-align: left;">
<li><span style="font-family: Verdana, sans-serif;">Consumption of 3600 Units (kWh) per year</span></li>
<li><span style="font-family: Verdana, sans-serif;">3 days backup</span></li>
<li><span style="font-family: Verdana, sans-serif;">CUF (Capacity Utilization factor) of 15%. See <a href="http://www.cercind.gov.in/2011/Whats-New/PERFORMANCE%20OF%20SOLAR%20POWER%20PLANTS.pdf">this link</a> for CUF in various parts of India. Number of units produced = Installed Capacity (in kW) * 24 * CUF. For e.g, a 1 kW panel with 15% CUF produces 3.6 kWh per day.</span></li>
<li><span style="font-family: Verdana, sans-serif;">70% battery usage (batteries cannot be fully drained)</span></li>
</ul>
<b><u><span style="font-family: Verdana, sans-serif;">Calculations</span></u></b><br />
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<span style="font-family: Verdana, sans-serif;"><br /></span></div>
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<span style="font-family: Verdana, sans-serif;"><b><i>How many solar panels?</i></b></span></div>
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<span style="font-family: Verdana, sans-serif;">1kW panel produces about 3.6 kWh per day (15% CUF). kWh produced in 1 year = 3.6*365 = 1314.</span></div>
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<span style="font-family: Verdana, sans-serif;">So ~ 3 kW panels are required.</span></div>
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<span style="font-family: Verdana, sans-serif;"><br /></span></div>
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<span style="font-family: Verdana, sans-serif;"><b><i>How many batteries?</i></b></span></div>
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<span style="font-family: Verdana, sans-serif;">Average daily requirement = 10 kWh.</span></div>
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<span style="font-family: Verdana, sans-serif;">A 12V, 200Ah battery holds about 2.4 kWh (Voltage * Ah/1000). Considering a cut-off at 70% this comes down to 1.68 kWh.</span></div>
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<span style="font-family: Verdana, sans-serif;">So the number of batteries required is</span></div>
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<span style="font-family: Verdana, sans-serif;">-- 6 for 1 day backup</span></div>
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<span style="font-family: Verdana, sans-serif;">-- 12 for 2 days backup</span></div>
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<span style="font-family: Verdana, sans-serif;">-- 18 for 3 days backup</span></div>
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<span style="font-family: Verdana, sans-serif;"><br /></span></div>
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<span style="font-family: Verdana, sans-serif;"><b><i>What is the rating of the Inverter?</i></b></span></div>
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<span style="font-family: Verdana, sans-serif;">Peak load may be higher than 3kW. So we need at least a 5kW inverter. Inverter also should support high initial surge current (for e.g if you run a water pump).</span></div>
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<span style="font-family: Verdana, sans-serif;"><br /></span></div>
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<span style="font-family: Verdana, sans-serif;"><b><i>How many charge controllers?</i></b></span></div>
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<span style="font-family: Verdana, sans-serif;">This depends on how the panels are divided into banks. I will assume a 48V/30A solar charge controller. ~3 would be required (48 * 30 = 1440 W. So for 3kW, at least 3)</span></div>
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<span style="font-family: Verdana, sans-serif;"><br /></span></div>
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<span style="font-family: Verdana, sans-serif;"><b><u>Cost (INR)</u></b></span></div>
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<span style="font-family: Verdana, sans-serif;"><i>Total cost</i> = Cost of (Panels + Batteries + Inverter + Charge controller + Installation + Other(transport etc))</span></div>
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<ul style="text-align: left;">
<li><i style="font-family: Verdana, sans-serif;">Cost of panels</i><span style="font-family: Verdana, sans-serif;"> = ~60,000 /kW (See this </span><a href="http://www.eai.in/club/users/aathmika/blogs/541" style="font-family: Verdana, sans-serif;">link</a><span style="font-family: Verdana, sans-serif;">. I've added 50% for retail price) = 1,80,000</span></li>
<li><span style="font-family: Verdana, sans-serif;">Cost of batteries = </span><a href="http://www.priceindia.in/consumer-electronics/inverter-battery-price/" style="font-family: Verdana, sans-serif;">11,000</a><span style="font-family: Verdana, sans-serif;"> per battery. 1 day backup price = 66,000. 2 days = 1,32,000, 3 days = 1,98,000</span></li>
<li><span style="font-family: Verdana, sans-serif;">Cost of inverter = ~<a href="http://www.alibaba.com/trade/search?fsb=y&IndexArea=product_en&CatId=&SearchText=5kw+solar+inverter">50,000</a> (Couldn't get an exact price online)</span></li>
<li><span style="font-family: Verdana, sans-serif;">Cost of charge controllers = </span><a href="http://rajelectronics.tradeindia.com/solar-charge-controller-409841.html" style="font-family: Verdana, sans-serif;">20,700</a><span style="font-family: Verdana, sans-serif;"> * 3 = 62,100</span></li>
<li><span style="font-family: Verdana, sans-serif;">Other costs: Structure for installing panels, Transport, Cables, Combiners, Man power etc </span></li>
<li><span style="font-family: Verdana, sans-serif;">Total cost = 1,80,000 + 1,98,000 + 50,000 + 62,100 + other cost (say 10% extra) = ~4,90,000 + 10% = ~ 5,40,000</span></li>
</ul>
</div>
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<span style="font-family: Verdana, sans-serif;">Even if we consider just 1 day backup, the cost is around 4,00,000.</span></div>
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<span style="font-family: Verdana, sans-serif;"><br /></span></div>
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<span style="font-family: Verdana, sans-serif;">On an investment of 5,40,000, one can save (if all goes well. There are various other risks that I have not considered) 3600 kWh per year. Assuming a grid price of INR 5/kWh, the annual return is INR 18,000 (3.3%). This, for me is "very expensive" and not a viable option.</span></div>
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Sumanth Kavurihttp://www.blogger.com/profile/11033407265529189813noreply@blogger.com1tag:blogger.com,1999:blog-5412325143823769449.post-59502355687942500802012-10-27T20:22:00.000+05:302012-10-27T20:22:36.397+05:30Solar power for homes<div dir="ltr" style="text-align: left;" trbidi="on">
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<span style="font-family: Verdana, sans-serif;">Power shortage and blackouts in various parts on India in 2012 made me think about solar power generation at home. I had various questions in my mind: How to produce solar power?, What is the cost and return on investment? etc.</span></div>
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<span style="font-family: Verdana, sans-serif;">I will try to answer the first question in this article.</span></div>
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<span style="font-family: Verdana, sans-serif;"><b>Introduction</b></span></div>
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<span style="font-family: Verdana, sans-serif;">Electricity can be generated from sunlight using photovoltaic cells<a href="http://en.wikipedia.org/wiki/Solar_power"><span style="font-size: xx-small;">[1]</span></a>. The amount of power generated depends on various factors like solar radiation received, efficiency of the solar cells, temperature etc. </span></div>
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<span style="font-family: Verdana, sans-serif;">Photovoltaic cells produce DC power. Most of the home appliances run on AC power. So a DC to AC inverter is required to use the solar power. </span></div>
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<span style="font-family: Verdana, sans-serif;">As solar power is not available during night, batteries are required if backup is desired.</span></div>
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<span style="font-family: Verdana, sans-serif;"><br /></span></div>
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<span style="font-family: Verdana, sans-serif;"><b>Various options for using solar power at home</b></span></div>
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<span style="font-family: Verdana, sans-serif;">Solar power system can be of different types: off-grid(not connected to external electricity supply) or on-grid, with or without battery backup. I've considered the following:</span></div>
<div>
<ol style="text-align: left;">
<li><span style="font-family: Verdana, sans-serif;">Off-grid + battery backup</span></li>
<li><span style="font-family: Verdana, sans-serif;">On-grid - battery backup</span></li>
<li><span style="font-family: Verdana, sans-serif;">On/Off grid + battery backup</span></li>
</ol>
<div>
<span style="font-family: Verdana, sans-serif;"><b>Off-grid + battery backup</b></span></div>
</div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgIlKMF6z1h2zWWRmHuCn2NpyUrqn1YBCrpNFxd7kOGHcHzAoRbRWT0lNj8w2r-Jm9VcP4Fr7KVlom_wQ6uvMswL-vz-fa4D9jp3syXVfn_vHkjM70eVaDHwNp7G48BN5xK3EIaqz2tRVA/s1600/Solar_basic.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="204" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgIlKMF6z1h2zWWRmHuCn2NpyUrqn1YBCrpNFxd7kOGHcHzAoRbRWT0lNj8w2r-Jm9VcP4Fr7KVlom_wQ6uvMswL-vz-fa4D9jp3syXVfn_vHkjM70eVaDHwNp7G48BN5xK3EIaqz2tRVA/s320/Solar_basic.jpg" width="320" /></a></div>
<div>
<span style="font-family: Verdana, sans-serif;">The power generated by solar panel is used charge the batteries. A charge controller is required to cut-off the power when the batteries are fully charged. </span><span style="font-family: Verdana, sans-serif;">The output of the batteries is fed into a inverter which converts DC(e.g: 12V,48V etc) to 230V, 50HZ AC. This can be fed to the home appliances.</span></div>
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<span style="font-family: Verdana, sans-serif;"><br /></span></div>
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<span style="font-family: Verdana, sans-serif;"><b>On-grid without battery backup</b></span></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhehxZKuPf_E4bqRW3TgFnlQzH6bLrU8E8Ratq29UbUDnl_wwzymYRZk2DyNK0wLM_ZYakVXIDfur47aglPqLCyHG7yvlCO2KfQE-ZJtMmEyNq8SaVFOz_GsF1r7niIZ6898Dl3FqSHYf0/s1600/Solar_on_grid.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="205" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhehxZKuPf_E4bqRW3TgFnlQzH6bLrU8E8Ratq29UbUDnl_wwzymYRZk2DyNK0wLM_ZYakVXIDfur47aglPqLCyHG7yvlCO2KfQE-ZJtMmEyNq8SaVFOz_GsF1r7niIZ6898Dl3FqSHYf0/s320/Solar_on_grid.jpg" width="320" /></a></div>
<div>
<span style="font-family: Verdana, sans-serif;">This system makes use of an on-grid inverter. This works in 3 different ways:</span></div>
<div>
<ol style="text-align: left;">
<li><span style="font-family: Verdana, sans-serif;">If power from panel == load, no power is drawn from the grid.</span></li>
<li><span style="font-family: Verdana, sans-serif;">If power from panel > load, remaining power is supplied to the grid.</span></li>
<li><span style="font-family: Verdana, sans-serif;">If power form panel < load, balance power is drawn from the grid.</span></li>
</ol>
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<span style="font-family: Verdana, sans-serif;">Power can be supplied to the grid only if the local power company permits you to do so. This is called <a href="http://en.wikipedia.org/wiki/Net_metering">net-metering</a> and is available in some countries(now aware of such policy in India).</span></div>
</div>
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<span style="font-family: Verdana, sans-serif;"><b><br /></b></span></div>
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<span style="font-family: Verdana, sans-serif;"><b>On/Off Grid with battery backup</b></span></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhR9WNYaW03OGfZl0xdhhlUW1NOkhPYxddLvJpnR1KIH0kYs5X3DVY_z5LsSM-wFicp9DCHAQ70rdWGHWMczHcjZ06e_uejkWMD58kV8r2f9y3wEPNhuptgqtnCQqLJHqoV55pwE3NO4Ro/s1600/Solar_on_off_grid.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="205" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhR9WNYaW03OGfZl0xdhhlUW1NOkhPYxddLvJpnR1KIH0kYs5X3DVY_z5LsSM-wFicp9DCHAQ70rdWGHWMczHcjZ06e_uejkWMD58kV8r2f9y3wEPNhuptgqtnCQqLJHqoV55pwE3NO4Ro/s320/Solar_on_off_grid.jpg" width="320" /></a></div>
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<span style="font-family: Verdana, sans-serif;">As the name suggests, this is a mix of the first two options. The difference from option 2 is that this charges the batteries first and supplies to the grid only after the batteries are fully charged. The power from batteries can be used when both solar power and grid power are unavailable.</span></div>
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<span style="font-family: Verdana, sans-serif;"><br /></span></div>
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<span style="font-family: Verdana, sans-serif;"><b>Comparison of various options</b></span></div>
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<span style="font-family: Verdana, sans-serif;">I've compared the various options on the following parameters:</span></div>
<div>
<ol style="text-align: left;">
<li><span style="font-family: Verdana, sans-serif;">Investment cost</span></li>
<li><span style="font-family: Verdana, sans-serif;">Utilization (whether 100% solar power received can be used)</span></li>
<li><span style="font-family: Verdana, sans-serif;">Maintenance cost</span></li>
<li><span style="font-family: Verdana, sans-serif;">Limitations</span></li>
</ol>
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<span style="font-family: Verdana, sans-serif;"><br /></span></div>
</div>
</div>
<table border="1">
<tbody>
<tr>
<td></td>
<td><b><span style="font-family: Verdana, sans-serif;">Installation Cost</span></b></td>
<td><b><span style="font-family: Verdana, sans-serif;">Utilization</span></b></td>
<td><b><span style="font-family: Verdana, sans-serif;">Maintenance Cost</span></b></td>
<td><b><span style="font-family: Verdana, sans-serif;">Limitations</span></b></td>
</tr>
<tr>
<td><span style="font-family: Verdana, sans-serif;">Off-grid</span></td>
<td><span style="font-family: Verdana, sans-serif;">Very High (due to batteries)</span></td>
<td><span style="font-family: Verdana, sans-serif;">< 100%</span></td>
<td><span style="font-family: Verdana, sans-serif;">High (due to batteries)</span></td>
<td><span style="font-family: Verdana, sans-serif;">Requires very high capacity</span><br />
<span style="font-family: Verdana, sans-serif;">to replace grid (4KW for every 1KW load)</span></td>
</tr>
<tr>
<td><span style="font-family: Verdana, sans-serif;">On-grid</span></td>
<td><span style="font-family: Verdana, sans-serif;">Medium</span></td>
<td><span style="font-family: Verdana, sans-serif;">100%</span></td>
<td><span style="font-family: Verdana, sans-serif;">Low</span></td>
<td><span style="font-family: Verdana, sans-serif;">Net-metering is not available in India</span></td>
</tr>
<tr>
<td><span style="font-family: Verdana, sans-serif;">On/Off-grid</span></td>
<td><span style="font-family: Verdana, sans-serif;">Medium to high (depends on batteries)</span></td>
<td><span style="font-family: Verdana, sans-serif;">Close to 100%</span></td>
<td><span style="font-family: Verdana, sans-serif;">High (due to batteries)</span></td>
<td><span style="font-family: Verdana, sans-serif;">Net-metering is not available in India.</span></td>
</tr>
</tbody></table>
<span style="font-family: Verdana, sans-serif;"><br /></span>
<b><span style="font-family: Verdana, sans-serif;">Conclusion</span></b><br />
<span style="font-family: Verdana, sans-serif;">An off-grid system is too expensive and seems to impractical for home use. </span><span style="font-family: Verdana, sans-serif;">On-grid system is the least expensive and utilizes all the power generated but requires a government policy to buy the power back. If backup is desired an On/Off-grid system with limited backup (to keep the cost under control) would be recommended.</span><br />
<span style="font-family: Verdana, sans-serif;"><br /></span></div>
Sumanth Kavurihttp://www.blogger.com/profile/11033407265529189813noreply@blogger.com0