tag:blogger.com,1999:blog-66553023040935225022024-03-20T04:21:51.480-07:00My Solar HomeInstalling solar panels
for my home in
Puerto Rico.Jonathan Friedmanhttp://www.blogger.com/profile/00241523238227442255noreply@blogger.comBlogger11125tag:blogger.com,1999:blog-6655302304093522502.post-25904678092949371712010-11-25T10:49:00.000-08:002010-11-25T10:56:17.525-08:00net meteringOur net metering system was installed on October 18. We can now see when the meter is going backwards, how much we have consumed and how much we have produced in excess of our consumption (that is, when the meter goes backwards). That is nice. Our 2 kW system has averaged about 2 kWh per day over consumption for the first 5 weeks. That is in contrast with an average daily consumption of just under 12 kWh. The way the billing here works, we will get charged the 22.9¢ per kWh for about 12 kWh per day and get back 10¢ x 2 kWh per day.<div><br /></div><div>One issue that just came up with the first bill, however. That gives a consumption of 901 kWh during late September and October, more than double our actual consumption. It is clearly a mistaken reading that requires correction, and I will lose a day trying to get it fixed. </div>Jonathan Friedmanhttp://www.blogger.com/profile/00241523238227442255noreply@blogger.com0tag:blogger.com,1999:blog-6655302304093522502.post-55584958550575992172010-04-03T10:47:00.000-07:002010-04-03T11:00:40.742-07:00Solar cells and shade<div>One critical element to understanding photovoltaic performance is that solar cells are current sources. This means that when you connect them in series, the weakest cell will determine the total current. In many (most?) solar panels, the individual solar cells are connected in series. For example, our 28V panels consist of </div><div>60 cells, each producing about 0.48V, connected in series. One shaded cell on a panel will determine the power output of the whole panel. </div><div><br /></div><div>For example, our 28V, 200W panels produce about 7A per panel under full sun. However, 50% shading of a single cell causes its output to fall to 3.5A, which drags the output of the whole panel down to 3.5A. This is why you often see descriptions of 10% shading costing 50% output. Basically, shading causes the current-voltage (I-V) curve of the solar cell to drop (lower current for same voltage output). This is why all </div><div>modern solar cells should have bypass diodes. The resistive nature of the underperforming cell produces a reverse bias on that cell, and the bypass diode conducts, providing a shunt for the excess current produced by the fully performing cells. (That said, although <a href="http://www.canadian-solar.com/">Canadian Solar</a> does say our panels have bypass diodes, they do not say whether each cell has a bypass diode, or if there is a single bypass diode for each panel.) A nice graphic description of how this works can be found on <a href="http://pvcdrom.pveducation.org/MODULE/Bypass.htm">this web site</a>.</div><div><br /></div><div>Still, partial shading is quite costly. For this reason, there are devices that will adjust the maximum power point (MPP)<sup>1</sup> of a panel to up the overall output in the face of partial shading or under-performance. These are called <a href="http://en.wikipedia.org/wiki/Power_optimizer">"Power Optimizers"</a>. Some examples of these are the <a href="http://www.solarmagic.com/">SolarMagic</a>, which is produced by <a href="http://www.national.com/">National Semiconductor</a>, and <a href="http://xandexsolar.com/">SunMizer from Xandex Solar</a>. Unfortunately, these are pretty expensive ($200 or more).</div><div><br /></div><div><a href="http://en.wikipedia.org/wiki/File:Solar_cell_equivalent_circuit.svg"><img style="float:left; margin:0 10px 10px 0;cursor:pointer; cursor:hand;width: 200px; height: 106px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjFi4kR-ipk2KoQ07PHTMMm956d4WMMi21FbUxJ65swY51VIYA81ZNfAIcvPIvEk3cNlwA8q2PnRxRAQM65EMnx6HB3Ms4uDdFv8M3PLNSZ6Z8cndJ6cL4-Tp_DxJuuLLPbJy_lXiXHi8U/s200/601px-Solar_cell_equivalent_circuit.svg.png" border="0" alt="" id="BLOGGER_PHOTO_ID_5455969723316984706" /></a></div><div>(For those more technically oriented, here is a solar cell equivalent circuit, which I found on <a href="http://www.wikipedia.org/">Wikipedia</a>.)</div><div><br /></div><div>It is a good question whether, with bypass diodes, Power Optimizers are helpful. As I mention in the previous paragraph, a bypass diode will not kick in unless the voltage across a cell is reversed. At MPP, a cell is performing optimally for the quantity of sunlight it receives and may still be boosting the system voltage, which removes the diode. </div><div><br /></div><div><br /></div><div><sup>1</sup>Maximum Power Point (MPP) is the location on a photocell I-V curve at which maximum power is produced. There is a <a href="http://zone.ni.com/devzone/cda/tut/p/id/8106">nice explanation</a> of MPP tracking on the <a href="http://www.ni.com/">National Instruments</a> website.</div><div><br /></div><div><b>Some resources on shade and photovoltaic performance</b></div><div><a href="http://www.energysavingproductsinfo.com/energy-saving-products/465-shading-and-solar-panel-efficiency/">Shading and Solar Panel Efficiency</a></div><div><a href="http://www.renewableenergyworld.com/rea/news/article/2009/02/shade-happens-54551">Shade Happens, by Ralf J. Muenster</a></div><div><br /></div>Jonathan Friedmanhttp://www.blogger.com/profile/00241523238227442255noreply@blogger.com0tag:blogger.com,1999:blog-6655302304093522502.post-29218620309000524972010-04-03T10:41:00.000-07:002010-04-03T10:47:21.741-07:00Some details on our installation<a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgZpxPpuyTeuUw6hXW2QIc7GjgiBH2rbN4zAz5Sy7CoB_uHQhGQRfmylyViTiPagR7T9YRse-TXAoqhoq-QUY-jpz_865yNRVQB_IMtEfKmF2ZD0po_5xCkn22mp64TLXzYi2WhspKnRAE/s1600/Photovoltaic_Block_Diagram.jpg"><img style="float:left; margin:0 10px 10px 0;cursor:pointer; cursor:hand;width: 230px; height: 186px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgZpxPpuyTeuUw6hXW2QIc7GjgiBH2rbN4zAz5Sy7CoB_uHQhGQRfmylyViTiPagR7T9YRse-TXAoqhoq-QUY-jpz_865yNRVQB_IMtEfKmF2ZD0po_5xCkn22mp64TLXzYi2WhspKnRAE/s320/Photovoltaic_Block_Diagram.jpg" border="0" alt="" id="BLOGGER_PHOTO_ID_5455968375188544994" /></a><br />Here is a circuit diagram of our solar installation. <div>It consists of 10 panels connected in series, each producing about 28 V. These consist of 60 cells also connected in series, so we have 600 solar cells in a series connection, producing over 280 V DC. This is then inverted in the SMA Sunny Boy 4000US grid-tie inverter. </div><div><br /></div><div>In my next post, I will talk about some of the headaches of having the cells connected in series, namely, the problem of shade. </div>Jonathan Friedmanhttp://www.blogger.com/profile/00241523238227442255noreply@blogger.com0tag:blogger.com,1999:blog-6655302304093522502.post-53023167249744348102010-03-06T07:36:00.000-08:002010-03-06T07:44:58.049-08:00Dealing with Hacienda<div><span class="Apple-style-span" style="font-size:large;"><b><span class="Apple-style-span" style="font-family:'lucida grande';">Solar Blog Entry - Dealing with Hacienda</span></b></span></div><div><br /></div><div><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">Dealing with the Puerto Rico tax office </span></span><i><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">Hacienda</span></span></i><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;"> is an important element of an alternative energy installation. The tax credit for tax year 2009 is 50%, which we expect to qualify for.</span></span></div><div><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;"><br /></span></span></div><div><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">It was important for us for our file to be opened in 2009, as many of the required documents took time to obtain and were not finally submitted until early January 2010. All of these documents need to be submitted in person to office 624B of the </span></span><i><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">Divisíon de Opiniones Administrativas y Legislación del Negociado de Asistencia Contributiva y Consultas Especializada</span></span></i><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;"> (that mouthful translates roughly to the Division of Administrative Opinions and Legislation of the Office of Tax Assistance and Specialized Consultations). Some are submitted by the installer and others by the customer, as I summarize below.</span></span></div><div><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;"><br /></span></span></div><div><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">1. First, they require demonstration that the taxpayer/customer has no debts to any government office or agency. For this, they require </span></span><i><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">Certificaciones Negativas de Deuda</span></span></i><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">, or Negative Debt Certificates from ...</span></span></div><div><span class="Apple-tab-span" style="white-space:pre"><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;"> </span></span></span><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">- Department of </span></span><i><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">Hacienda</span></span></i><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;"> (tax office) </span></span></div><div><span class="Apple-tab-span" style="white-space:pre"><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;"> </span></span></span><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">This can be obtained from the local </span></span><i><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">Hacienda</span></span></i><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;"> office or online from </span><a href="http://pr.gov/"><span class="Apple-style-span" style="font-size: medium;">http://pr.gov</span></a><span class="Apple-style-span" style="font-size: medium;">.</span></span></div><div><span class="Apple-tab-span" style="white-space:pre"><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;"> </span></span></span><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">- </span></span><i><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">Centro de Recaudaciín de Ingresos Municipales</span></span></i><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">, or CRIM (Municiple Property Tax Office), which refer to property taxes.</span></span></div><div><span class="Apple-tab-span" style="white-space:pre"><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;"> </span></span></span><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">This must be obtained from the local CRIM office (have fun :-)).</span></span></div><div><span class="Apple-tab-span" style="white-space:pre"><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;"> </span></span></span><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">- </span></span><i><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">Departamento de Trabajo y Recursos Humanos</span></span></i><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;"> (Department of Labor and Human Resources), which requires communicating with the central office in San Juan but can be carried out via FAX. This is automatic for a home installation, if you are not a business owner and have no relationship with this department.</span></span></div><div><span class="Apple-tab-span" style="white-space:pre"><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;"> </span></span></span><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">We discovered that our local office in Arecibo could not provide this, and we called the main office in San Juan at 787-754-5818 who asked us to FAX the required information (photocopy of my drivers license and social security number along with an address of where to send the certification) to 787-281-5649.</span></span></div><div><span class="Apple-tab-span" style="white-space:pre"><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;"> </span></span></span><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">- </span></span><i><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">Corporación del Fondo del Seguro del Estado</span></span></i><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;"> (State Insurance Fund Corporation), which, for a modest annual fee, provides accident and injury coverage for home and business owners who contract work on their property.</span></span></div><div><span class="Apple-tab-span" style="white-space:pre"><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;"> </span></span></span><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">We went to our local </span></span><i><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">Fondo</span></span></i><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;"> office for this certification.</span></span></div><div><span class="Apple-tab-span" style="white-space:pre"><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;"> </span></span></span><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">- ASUME, which is the office that monitors legal obligations such as child support and alimony payments.</span></span></div><div><span class="Apple-tab-span" style="white-space:pre"><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;"> </span></span></span><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">We received this certification at the local ASUME office, which was the most efficient of all the offices we visited.</span></span></div><div><span class="Apple-tab-span" style="white-space:pre"><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;"> </span></span></span><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">- and if the installation is for a business, such certifications must be obtained from its investors and partners who own over 25% of the company's shares or represent over 25% of its operations.</span></span></div><div><span class="Apple-tab-span" style="white-space:pre"><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;"> </span></span></span><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">Happily, we did not have to do this one.</span></span></div><div><span class="Apple-tab-span" style="white-space:pre"><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;"> </span></span></span></div><div><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">2. Second, you have to deliver certification of tax filings, which are obtained from </span></span><i><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">Hacienda</span></span></i><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">. If there is a partnership involved, such as for a business with investors and/or partners, they must also obtain these certifications.</span></span></div><div><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;"><br /></span></span></div><div><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">3. The Installer should be responsible to submit the Photovoltaic Equipment Certifications (</span></span><i><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">Certificados de de Equipos Fotovoltaicos</span></span></i><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">) filed by the </span></span><i><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">Administración de Asuntos Energéticos</span></span></i><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;"> (Energy Issues Administration of </span></span><i><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">Hacienda</span></span></i><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">) (AAE).</span></span></div><div><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;"><br /></span></span></div><div><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">4. The Installer Certificate must be provided, same as that issued by the AAE. This is also responsibility of the Installer.</span></span></div><div><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;"><br /></span></span></div><div><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">5. The Installer should submit a "Design and Installation of Photovoltaic System" certificate, again issued by the AAE.</span></span></div><div><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;"><br /></span></span></div><div><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">6. A copy of the Commercial Invoice from the Installer (i.e. the receipt for the installation, including both parts and labor, from the Installer to the Customer).</span></span></div><div><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;"><br /></span></span></div><div><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">7. Any other document the petitioner considers relevant.</span></span></div><div><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;"><br /></span></span></div><div><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">All of these documents must be delivered within a period of 60 days. Our process began December 14 and ended on January 25. Once delivered, </span></span><i><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">Hacienda</span></span></i><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;"> evaluates the case and submits a determination of whether the project qualifies for the tax credit. We are currently awaiting that determination, which we hope to have in time for filing our taxes in April.</span></span></div><div><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;"><br /></span></span></div><div><span class="Apple-style-span" style="font-family:arial;"><span class="Apple-style-span" style="font-size: medium;">My next post will summarize the first month of performance of our photovoltaic system.</span></span></div>Jonathan Friedmanhttp://www.blogger.com/profile/00241523238227442255noreply@blogger.com0tag:blogger.com,1999:blog-6655302304093522502.post-70758308465887964652009-12-24T03:44:00.000-08:002009-12-28T04:43:42.522-08:00<div>Our solar installation is nearly complete, and with that in mind, I have been looking into some of the more subtle, yet quite important, issues </div><div>of photovoltaic installations. Foremost among these is the problem of shade.</div><div>Shade can have an impact that is surprisingly disproportional to its apparent coverage. This is because of the construction of a sol</div><div>ar panel. A given panel generally consists of dozens of cells connected in series. If one of those cells is shaded, it may not only not contribute to the output of the panel, it may detract from it by becoming a resistive element. The impact of one non-contributing cell of the dozens in a panel can be as much as 50% of the panel output (see these links: <a href="http://www.renewableenergyworld.com/rea/news/article/2009/02/shade-happens-54551">http://www.renewableenergyworld.com/rea/news/article/2009/02/shade-happens-54551</a>, <a href="http://www.energysavingproductsinfo.com/">http://www.energysavingproductsinfo.com/</a>, <a href="http://www.greenlivingtips.com/articles/237/1/Solar-panel-basics.html">http://www.greenlivingtips.com/articles/237/1/Solar-panel-basics.html</a>, and there are lots of others).</div><div>There are a number of ways solar panel manufacturers try to limit the effects of shade. Bypass diodes are one of the most common, but it is surprisingly difficult to find much information on how these are employed. (<a href="http://www.absak.com/tech/diodes.pdf">Here is a link to a simplistic explanation.</a>) For example, our <a href="http://www.canadian-solar.com/en/products/standard-modules/cs6-series.html">CS6p-200p</a> panels have bypass diodes, but none of the documentation states how many are in the panel. These function by passing current when a cell becomes resistant, but when the cell is operating the diode is reverse biased, and therefore resistant. There are also higher-tech solutions, such as <a href="http://www.solarmagic.com/">SolarMagic®</a>, from</div><div> National Semiconductor, which acts as a voltage regulator. It has two benefits: first, to regulate the panel voltage level so that it continues to contribute to the overall output of the installation, and second, to report on the panel performance, which helps to identify when a panel is under-performing.</div><div>Shade is a problem for us in the morning, which is when Puerto Rico receives the most reliable sun (afternoons tend to get convection-generated clouds). There is a ridgeline just east of us that has many tall trees. We have trimmed some of these and will have to trim more. By mid-morning, the sun is above the trees.</div><div>Finally, we just found out that the law will not allow us to turn on the system until we complete two final steps. These are certifications, one by </div><div>the design engineer and the other by the power company. The first is simple and should be done soon (with a slight Christmas delay). The second is hard to predict, as is everything having to do with government agencies. However, if the power company does not respond within 10 days of notification, we have the right to turn on the system ourselves.</div><div><a href="http://www.energymatters.com.au/">This website</a>, in Australia, has some useful tools if you are interested in the benefits of solar installation.</div><div>The following are a selection of photographs of our experience.</div><img style="float:left; margin:0 10px 10px 0;cursor:pointer; cursor:hand;width: 214px; height: 320px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjQmiZ4Xtau-3H3xcWCy5SFXnt3Lk2nElOyyZs8Jb7jS_jrWceqcN9R12EpVxrwH-9LatF5d9sB6GHeUfT6pV5RYVnmOA7OlB_qxXEfKLgDGVCyJhqtg6KwwyRcqPQ_wEMKU3TKbOzowHM/s320/IMG_3188.jpg" border="0" alt="" id="BLOGGER_PHOTO_ID_5418771054212544082" /> The pictures are:<div>1. The SMA Sunny Boy 4000US Inverter</div><div>2. The panels from below, showing the mounting</div><div> structure</div><div>3. The view from the ridge east of our house.</div><div><br /><div><img style="float:left; margin:0 10px 10px 0;cursor:pointer; cursor:hand;width: 320px; height: 214px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg7eYcM5q9cy1pYJqAifjwJkeOZfGrQBXjgEqDQ5Hr20yZOAilAFhNL5RtB35jwspOHzaUyVsnAIg4eiFSt_WjpASYYnFT80fDbpLmhLCbXV0vopZUdC2EvT6Hf4AjtZSYCNmVTXzmQ_6I/s320/IMG_3292.jpg" border="0" alt="" id="BLOGGER_PHOTO_ID_5418771315143407714" /></div><div><img style="float:left; margin:0 10px 10px 0;cursor:pointer; cursor:hand;width: 320px; height: 214px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhV768sc_J2NGFz2AzdgMG7m5q0NAvfFw7BYK4wc8KYlfOZD6L6vtFfw9X94hNz6J_DH65BgSjeOwTNJMPTqVJUGAEEBN2hszzaRzgmNlLW4iusNY8d4OG_s8jzDMU9Im-QGk95NPTFLx8/s320/IMG_3297.jpg" border="0" alt="" id="BLOGGER_PHOTO_ID_5418772093008017090" /></div></div>Jonathan Friedmanhttp://www.blogger.com/profile/00241523238227442255noreply@blogger.com0tag:blogger.com,1999:blog-6655302304093522502.post-84941099671561313672009-11-20T14:02:00.000-08:002009-11-20T14:03:58.724-08:00hardware is here!We have just received 10 200-W solar panels and the 4 kW inverter. I will post photos soon. We are aiming for installation the first week of December.Jonathan Friedmanhttp://www.blogger.com/profile/00241523238227442255noreply@blogger.com0tag:blogger.com,1999:blog-6655302304093522502.post-70635094940465025542009-11-12T05:43:00.000-08:002009-11-12T05:55:46.174-08:00tax credits for Puerto Rico solar power installations<div>Prior to the passage of law 248, the Puerto Rico legislature created the<a href="http://www.ads.gobierno.pr/Programa_PV_AAE/"> </a><i><a href="http://www.ads.gobierno.pr/Programa_PV_AAE/">Administración de Asuntos Energéticos</a></i><a href="http://www.ads.gobierno.pr/Programa_PV_AAE/"> (AAE)</a> to monitor and regulate solar electricity installations in Puerto Rico.</div><div><br /></div>I read <a href="http://www.lexjuris.com/lexlex/Leyes2008/lexl2008248.htm">law 248 of 2008</a> (in Spanish) last night. There are a few useful points to highlight.<div>1. The 75% credit was during Puerto Rico fiscal years 2007-2008 and 2008-2009.</div><div>2. The 50% credit applies for FYs 2009-2010 and 2010-2011.</div><div>3. After FY2010-2011, the tax credit is 25%, and this seems to extend for an indefinite period.</div><div>4. The credit applies to both the equipment and installation, although it also applies only to equipment that carries 5 years or more warranty.</div><div>5. The equipment must be installed and certified by solar-licensed electricians and engineers.</div><div>6. The tax credit can be carried over for up to 10 years, so if for some reason you cannot receive some or all of the credit in one year, you can carry it over to the next, for up to 10 maximum. This may be important, as the total available in tax credits for any given FY is limited.</div><div>7. The tax credit can be transferred once. </div><div>8. Apparently, the documents that are required for the tax credits must be submitted with one's tax returns for 6 years following the installation.</div><div>9. The sales tax (the famous IVU) does not apply to the acquisition of solar electric equipment.</div><div><br /></div><div>Later, I will detail the process of applying for the tax credit.</div>Jonathan Friedmanhttp://www.blogger.com/profile/00241523238227442255noreply@blogger.com0tag:blogger.com,1999:blog-6655302304093522502.post-64435843221817356882009-11-12T05:26:00.000-08:002009-11-12T05:42:44.115-08:00finalizing specificationsChoosing a grid-tied system has its costs. The main one is that when the utility power goes down, so does the solar electricity. This is for several reasons. First, "grid tied" means what it says, tied to the grid, not to the house. It serves to mitigate some or all of the use of grid power, but the house still runs off the grid. Second, the house cannot run off power from the panels alone (inverted, of course). This is because of the fact of brownouts caused by clouds passing in front of the sun, or surges in demand. So a storage system is required as a buffer. This consists of a battery bank, which I decided against for reasons detailed below.<div><br /></div><div>Our contractor visited with the solar energy engineer on Tuesday. They measured the estimated average daily production based on the hours of sun that can be expected per day. This measurement consists of first, a device that records the sky exposure of the site. Based on the annually integrated solar track, shadowing from trees, adjacent buildings, even our TV aerial, cloud-cover data for our location, and other parameters, it computes a number that they claim is quite reliable. In our case, we will get an average of 5.4 h/day of production. This comes to 300 kW-h/month, which is just over half of our energy usage.</div><div><br /></div><div>We will purchase 2 kW in panels, but with a 4 kW inverter, so if we choose to add capacity, it means only additional panels. The panels are 200 W models from <a href="http://www.canadian-solar.com/">Canadian Solar</a>. The inverter is a <a href="http://www.SMA-America.com/">Sunny Boy 4000US</a>. The reason to forego the batteries that would have given us a standalone system is mostly cost. The batteries are expensive and short-lived. In fact, I calculated that whatever we save in electricity costs, we will spend in replacing battery cells, which have roughly 5-year lifetimes.</div><div><br /></div><div>Our contractor is <a href="http://www.prgreentech.com">PR Green Tech Corp</a>. Julio Correa, the owner, is friendly and attentive, and appears to be quite devoted to his avocation. I hope this will serve us into the future as technologies evolve.</div>Jonathan Friedmanhttp://www.blogger.com/profile/00241523238227442255noreply@blogger.com0tag:blogger.com,1999:blog-6655302304093522502.post-64906635791966783062009-10-03T04:08:00.000-07:002009-10-03T04:44:53.765-07:00restartAfter most of a year of delay, I have restarted my solar home project. <div>Yesterday (October 2), I gave a presentation on home solar power at a local parochial school, "Nuestra Señora de Carmen", in Hatillo, PR. I was very impressed by the abilities and interests of this group of 11<sup>th</sup> graders. They asked a lot of interesting questions, and in this post, I will begin to address them. We start with anticipated power cost savings. </div><div><br /></div><div>The simple calculation is to estimate how many kilowatt-hours per month my system will produce and how much electrical power will cost over the coming years. We are installing a 2kW system. We can reasonably expect to have full sun on the panels for 6 hours/day, 25 days per month, which adds up to 150 h/month. We currently pay 20¢ per kWh, so this will be worth $30/month. At this rate, we will reduce our electric bill by $360 a year, or $3600 over 10 years, and it will take about 20 years to pay off our ultimate construction cost, which is close to the 25-year 80% efficiency lifetime of the panels. (A total cost of $7200 includes the tax credit we expect to receive from the PR government.) In reality, it may take 25–30 years to pay off the system.</div><div><br /></div><div>The above calculation makes a big assumption: that electricity costs will not go up. However, only a little over a year ago we were paying close to 30¢ per kWh, and this cost will increase in the coming years. The question is, by how much? This is a big problem to estimate, as electric power costs do not change with any predictable pattern. We can assume that these costs have bottomed out, given the state of the economy, the environment, and of known reserves of petroleum (<a href="http://www.sunovpetroleum.com/2009/05/the-future-for-ep-costs/">see this link for estimates of future petroleum costs</a>) (in PR there are currently no other sources of electricity). If electrical power averages 30¢ per kWh over the next 10 years, we will save $5400 rather than $3600. </div><div><br /></div><div>I will do some more research on electricity costs. In future posts I will touch on changes in our plans, solar-thermal power, and wind power. </div>Jonathan Friedmanhttp://www.blogger.com/profile/00241523238227442255noreply@blogger.com0tag:blogger.com,1999:blog-6655302304093522502.post-43178725801706118412008-12-03T14:53:00.000-08:002008-12-03T15:07:56.082-08:00solar energy system componentsMy solar energy system is still taking shape, but here are the components I am looking at at this time, including some sample web sites that describe them:<br /><br />1. Panels: <a href="http://www.solardepot.com/pdf/Evergreen_Spruce_195.pdf">Evergreen Spruce 195W</a> — These are polycrystalline panels that we have chosen because of both their electrical and mechanical properties. I will try to spell these out in detail in a later post. We will mount them in sets of 3, to get 72 V and 585 W peak power. <br />2. <a href="http://www.solar-electric.com/charge_controls/mppt.htm">Battery charge controller</a> — The charge controller makes sure that the charging efficiency is maximized by regulating the charging voltage to the battery bank (48V) while minimizing power loss.<br />3. <a href="http://www.mkbattery.com/images/8L16-DEKA.pdf">Batteries</a> — These are a big issue, as we want to use the solar energy collected when the sun is down, but battery technologies are far behind the rest of the technologies we are considering, the costs are very high and stay high, as I estimate we will spend $800-1000 per year average to keep the battery banks at full strength. That is more than we expect to save from taking most of our electricity use off the grid.<br />4. <a href="http://www.solarelectricsupply.com/Inverters/Magnum/index.html">Inverter</a> — Inverter technology is very good these days. The inverter we have chosen is 4400W (model MS4448AE), which has 94% peak efficiency.<br />5. Automatic transfer switch<br /><br />There are a lot of options on the market, which is very good. I am still doing my homework to compare systems and technologies.Jonathan Friedmanhttp://www.blogger.com/profile/00241523238227442255noreply@blogger.com0tag:blogger.com,1999:blog-6655302304093522502.post-65251269453670323252008-11-30T05:19:00.000-08:002008-11-30T07:49:45.121-08:00My Solar Home<span style="font-weight:bold;">Web resources:</span><br />English:<br /><a href="http://www.dsireusa.org/library/includes/incentive2.cfm?Incentive_Code=PR09F&state=PR&State2=TR&CurrentPageID=1&RE=1&EE=1">Puerto Rico Incentives for Renewables and Efficiency<br /></a><br />Español<br /><a href="http://www.oslpr.org/DOWNLOAD/ES/2008/0248C3268.pdf">Ley 248 del 10 de agosto de 2008</a><br /><a href="http://www.hacienda.gobierno.pr/downloads/pdf/cartas/CC-08-13.pdf">Carta Circular Rentas Internas 08-13</a><br /><a href="http://environmenergy.com/db4/00351/environmenergy.com/_download/ResumendeLey248.pdf">Resumen de ley 248</a><br /><br /><span style="font-weight:bold;">Introduction</span><br />In August of this year (2008) the government of Puerto Rico announced tax incentives for the installation of solar energy systems in homes and businesses. These include both electricity and water heaters. They pay up to 75% of the cost through June 30, 2009, 50% during the following year, and 25% thereafter. Costs that exceed the taxpayer's tax liability can be carried over to following years, up to 10 years.<br /><br />My goal is to install a grid-tied solar electricity system to provide for most of my house most of the time. I hope to reduce my electricity use by 1/2, and I hope to sell a little back to the utility (at 10¢/kW-h). Here in Puerto Rico we have adequate to good sun all year, so this should work well. <br /><br />My home has a solar water heater, and I have been considering solar panels since we began building in 2002. This tax incentive has inspired me to move forward, though I have been studying the options for some time. An internet search identified a handful of solar energy retailers in Puerto Rico, and I send out several e-mail and webform inquiries. I received a response from PRGreenTech.com, and most of what follows came from that communication. I also have visited Casa Solar, PR in Bayamón.<br /><br />Julio Correa, of PR Green Tech, visited my home on November 21. I was concerned by the fact that there is a tree-covered hill to the east and many afternoons are cloudy, both of which may limit sun exposure, but Correa did not feel these were such important concerns. Sun will be on the panels by between 8:30 and 9:00, even in mid-winter, when the shading is worst, and we should typically have 4-6 hours of full sun. The fact that Puerto Rico is 18N latitude also helps.<br /><br />Correa works with 48 V DC systems, and the panels are 195 W, 24 V. Rather than connecting to the charging system in pairs, producing 48 V in full sun, he uses the panels in sets of 3, which will produce 48 V even in some degree of shade. The panels are polycrystalline, which, though they are less efficient, have two advantages: 1. they are more durable, and 2. (I understand that) their "turn-on" light level is lower than for monocrystalline (I have to confirm this).<br /><br />My house has a few items that produce heavy loads. We will exclude the one air conditioner, which will continue to connect directly to the grid. It is a 18,000 BTU/h unit, which is rated for 1950 W. That excluded, we still have the following:<br />1. A water (deep well) pump. We always use water from a 600 Ga reservoir, which is supplied from the aqueduct authority. This is because water supplies here are quite unreliable (we recently had 2+ weeks with no water during the day, and only a trickle at night). This pump is rated for 1500 W.<br />2. A microwave oven. Correa says these are among the biggest problems for solar inverters.<br />3. A toaster oven.<br />4. Blowdrier<br />Happily, our oven and cloths drier are both connected to gas. The solar water heater has an electrical backup, but if we are using that, it means there hasn't been sun for a while, so we will be running off the grid in any case.<br /><br />In future blog posts, I will describe the process by which we choose our solar energy system. These are divided up as follows:<br />1. Total power output of the panels.<br />2. Specifics of the charging system (voltage regulation)<br />3. Battery capacity (in A-h), costs etc. (batteries are not covered by the tax incentive law, so cost is critical)<br />4. Inverter capacity<br />5. Grid-tie system<br />6. Questions:<br /> - At what point in the battery depletion do we switch off the solar powered system and go to grid?<br /> - How much solar panel capacity is needed to provide sufficient charge to the batteries to run until charging re-commences?<br /> - How much energy consumption (A-h) will we need, and how to we convert that throughout the system?<br /> - How do we make sure the system is expandable, so we can add capacity later for running the air conditioner?Jonathan Friedmanhttp://www.blogger.com/profile/00241523238227442255noreply@blogger.com0