Solar Water Heater

<body topmargin=0 leftmargin=0 marginheight=0 marginwidth=0> <table cellpadding=0 cellspacing=0 border=0><tr> <td valign="top" colspan=2 height=90 BGCOLOR="#006699" TEXT="#080000" background="1fcfd5a3.jpg"> <div> <FONT SIZE="5" COLOR="#000000" FACE="Arial" ><B>BIT Company</B></FONT><B>    </B><B> </B><A HREF="id50.htm" TARGET="_top" TITLE="Greenhouses"><U><B>Greenhouse  </B></U></A><A HREF="id50.htm" TARGET="_top" TITLE="Greenhouses"><U><B>home</B></U></A></div> <div> </div> </td> </tr><tr> <td valign="top" width=210 BGCOLOR="#FFCC66" TEXT="#080000" background="1fdd2b03.jpg"> <div> <IMG SRC="28fa87d0.jpg" border=0 width="168" height="125" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <div>              Collector filled</div> <bR> <div> <IMG SRC="27db5870.jpg" border=0 width="181" height="135" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"> </div> <div>           Collector empty</div> </td> <td valign="top" height=390 BGCOLOR="#FFFFFF" TEXT="#080000"> <div> <I>Solar Water Heater</I></div> <div> (author's note: the following information is archival from 1991 and brought back by request. Some documentation is missing and will be added if found or interest is sufficient.)</div> <bR> <DIV ALIGN="LEFT"></DIV> <div> <B>A Low Cost High Efficiency Solar Water Heater</B></div> <bR> <div> <B>Introduction</B></div> <bR> <div> <B>The author's interest in alternate energy systems became serious upon returning to Florida from California in 1976. After six plus years in the benign climate of the Santa Clara Valley with very low cost natural gas and electricity, it was quite a shock to see the Florida rates and the summertime necessity for air conditioning and winter heating.</B></div> <bR> <div> <B>After several years of considering many designs, we built a two thousand square foot earth sheltered house which solved the majority of heating and cooling problems but the central atrium posed heat build-up problems in the summer. An interesting solution occurred to me several years ago and this paper will concern itself with the concept as applied to domestic hot water. </B></div> <bR> <bR> <div> <B>Technical Discussion:</B></div> <bR> <div> <B>Present practical commercially available solar water heaters tend to be primarily of the metal flat plate pressurized type with a thermostatically controlled circulation pump. Thermo-syphon systems are the best choice where the location of the collector can be below the storage tank, i.e.; split-level, sloped site, or two-story structures. All of the pressurized systems do need to be drained down under periods of prolonged cold and/or cloudiness and require owner or automatic control attention. The best of the automatic systems observed by the author was in a small domestic unit with a price tag of approximately $4,000 and still required the operator to occasionally manually defrost and drain in the event of the passage of a fast cold front.</B></div> <bR> <div> <B>The following pages will describe a lightweight freeze proof solar collector that can be commercially manufactured inexpensively.</B></div> <bR> <div> <B>There has always been the problem of cost, weight, and serviceability with all but the simplest of solar water heaters, which are not practical for normal household use. Refer to </B><FONT SIZE="3" COLOR="#0000FF" FACE="Arial" ><A HREF="id77.htm" TARGET="_top" TITLE="Solar water heater figure 1"><U><B><U>Figure 1</U></B></U></A></FONT><B> for the following description.</B></div> <bR> <div> <B>The collector consists of a 4' x 4' panel of GE's Thermoclear Lexan "R" or equivalent. It is designed with high temperature CPVC manifolds that can be easily ganged with additional collectors if required. See</B><A HREF="id78.htm" TARGET="_top" TITLE="Solar water heater figure 2"><U><B><U> </U></B></U></A><FONT SIZE="3" COLOR="#0000FF" FACE="Arial" ><A HREF="id78.htm" TARGET="_top" TITLE="Solar water heater figure 2"><U><B><U>Figure 2</U></B></U></A></FONT><B>.</B></div> <bR> <div> <B>As shown on the diagram, the heat exchanger is mounted on the exterior of the storage tank which can be any of many conventional gas or electric water heaters. It is a simple process to remove the shroud from the typical unit and apply the heat exchanger coils with thermally conductive epoxy.</B></div> <bR> <div> <B>One of the largest losses of energy in any solar water heater is in the heat transfer conduits from the collector to storage. Except for structures deliberately designed for solar heated water, the lines tend to be long and difficult to be efficiently insulated.</B></div> <bR> <div> <B>Vacuum insulated lines have been in common use for many decades in military, scientific, and industrial systems, but their high cost limits usefulness in domestic water heating systems. </B><FONT SIZE="3" COLOR="#0000FF" FACE="Arial" ><A HREF="id79.htm" TARGET="_top" TITLE="Solar water heater figure 3"><U><B><U>Figure 3</U></B></U></A></FONT><B> describes a simple vacuum insulated line with a vacuum "pump" that is easily owner maintainable and consumes no energy except for the original purging and whatever make-up might be needed over the years. As blackbody and reflectance characteristics are not specified for the materials listed, actual R factor cannot be accurately calculated but will far exceed any foam or fiber insulation. The author has looked at doing the same with the collector itself but the complexity of sealing the unit inexpensively renders this impractical. (</B><FONT SIZE="3" COLOR="#0000FF" FACE="Arial" ><A HREF="id80.htm" TARGET="_top" TITLE="Solar water heater figure 4"><U><B><U>Figure 4</U></B></U></A></FONT><FONT SIZE="3" COLOR="#111111" FACE="Arial" ><B>)</B></FONT></div> <bR> <div> <A HREF="id81.htm" TARGET="_top" TITLE="Solar Controller Panel"><U><B><U>Solar Controller Panel</U></B></U></A></div> <bR> <DIV ALIGN="LEFT"></DIV> <div> <B>Specifications</B></div> <bR> <div> <B>Thermoclear Solar Collector</B></div> <bR> <div> <B>Size                                       4' 1" x 4' 1" x 3.75"</B></div> <bR> <div> <B>Weight                                  dry - 26 lbs</B></div> <div> <B>                                               wet - 39 lbs</B></div> <bR> <div> <B>Efficiency (see note 1)     63+%</B></div> <bR> <div> <B>Heat transfer fluid             50/50 antifreeze/water with MTB dye</B></div> <div> <B>                   </B></div> <div> <B>BTU/hr (avg 9AM-3PM     3,528/hr,  21,168/6 hr. This is sufficient</B></div> <div> <B>                                               to supply 8.5 gal/hr or 51 gal/6 hr of </B></div> <div> <B>                                               hot water with an inlet  temp of 72 F</B></div> <div> <B>                                               and outlet  temp of 120 F (6.2 KWH)</B></div> <bR> <div> <B>                   </B></div> <div> <B>Maintenance                      wash cover as req'd </B></div> <bR> <div> <B>                    </B></div> <div> <B>Operating temperature    -30 F to +170 F</B></div> <bR> <div> <B>Note 1: External temp     50 F</B></div> <div> <B>              Wind velocity      10 MPH</B></div> <div> <B>              Inlet temp             110 F</B></div> <div> <B>              Outlet temp          140 F  </B></div> <bR> <bR> <bR> <bR> <bR> </td> </tr></table></body>