
                       LARTEC11.COM

 I have been working with solar systems for ten years now, but remember, 
 these words are solely my opinion and not anything else.

 I advise a thermal (heat absorbing), hydraulic solar system only.
 Your present heating system does'nt matter if it is in a good shape.
 Solar heating is useful anyway.
 If you don't have a hydraulic (hydronic) heating system, then make plans
 for switching to one at the time you need a major repair.
 (This does not apply for tropic areas thow).
 The reason is that you will be less sensitive to price fluctuations
 on the market, as you will be able to swop energy source.
 You will also be able to cut down heating cost far better than any other 
 system.

 If you consider purchasing a solar system, take this into account.
 Look for the orientation of the roof (or the collector mounting base).
 The deviation from south should not exceed 40 degrees (east or west).
 There shall not be a tree, or any other obstacles directly at collector
 front.
 You must have at least 6 hours shadowfree for your solar collector.
 The sun moves 15 deg/hour which means total 90 deg shadowfree.

 If your house meet these requirements, then there is a good chance you
 will make a farily short pay back period, and please proceed.

            About the solar simulation program.

 The program is applicable for hydraulic heat systems only.

 Free location. You can simulate any system in the world.
 Free mounting. Variables are: Location latitude, collector angle, azimut 
 (pointing angle) and area.
 Free use of accumulator volume and insulation.

 Free choice of solar collector mark and type.
 It is nessesary to have reliable data of the collector from an acredited
 solar collector testing institution.
 Shadowing trees or mountain peaks is taken to account.

 Weatherconditions is represented by medium daytime temperature, 
 (sun is visible) and medium night temp (sun invisible). 
 Bright sky or cloudy.
 It may be nessesary to update your weatherfiles, as default files origin
 is from a fairly cold area (Sundsvall).
 
 The sun radiation is calculated as a function of the elevation (sun height).
 As there is a lot of air to penetrate at low angles, the radiation also
 decrase along with the elevation.
 I have set 760 W/m2 at zero deg(ground level), and then increase by 
 270*sin(elevation) meaning 1030 W/m2 at zenit. This is farily accurate.
 At cloudy condition 110 W/m2 radiation is estimated all over the sky.
 
 The heating need is a function that start with no power at 17 C degree above
 freezing point(+17 C deg), or your  "37=INSULATION" typed figure.
 The starting point is in fact determined by the house insulation status.
 If you don't have it, leave it, the default value is sufficient.
 The steep is your figure of heating need at zero C degree.

 The solar collected energy is calculated from the data of the collector used, 
 and is metered at connection point, meaning no external heat losses is taken
 to account here. 

 The collector inlet = accumulator bottom temperature, and collector outlet =
 acc. topp temp plus 3 deg for heat exchanger heat loss.

 Accumulator temperature is affected from energy to or from the acc, at a 
 rate of 1.17 kWh/deg*m3(volume) pure water heat capacity is 
 4.18 W*s/g*C (Joule).
 It is also affected from internal heat losses, and 20 meter CU-piping 
 insulated by 10 mm Isoflex pipe insulation, this represent the piping from
 collector to acc. 220 W of flowpump effect is also withdrawn.

 At net solar energy, the acc temp is rising from the topp to the layer limit,
 and then topp and bottom rise simultaneous.
 From internal heat loss, and heating need, the bottom temp is falling to layer
 limit, and then both go down. The acc topp temp is never gonna fall below
 the preset minimum temp thow. 
 Either topp or bottom is ever falling below 20 C deg, as this is happening 
 under most rare conditions.
 
 If you have an integrated, internal solar pipe battery as heat exchanger, 
 6 deg heat loss is estimated, and the acc is heated from the bottom to equal 
 temp as the top. Else it is like above.

 There is a feature called "leveled flow valve temperature", and it's 
 function is, that the heating need determines the flow valve temperature,
 and the acc top temp is following, only framed by the limitations set by
 min temp and boiling temp. This is a good way to save heat energy, as you can 
 lower the acc temp when little energy is needed.

 All this is done to get the best possible image of reality from the 
 simulation.

 Hope you got some question marks straigthen out.
 
 Stig Larsson
