• Glazing should allow maximum solar energy to enter
but block heat from escaping to the ambient air.
• Absorber plate should capture as much solar energy as
• Provide insulation that will not absorb moisture under
the absorber plate to hold in as much energy as possible.
• Smaller flow tubes provide a larger surface area to
volume ratio which will heat the fluid better, but result in a
larger pressure loss which requires a bigger pump.
• The area of the collector is determined by the heat
requirements which are affected by the amount of sunlight
available, the volume of air in the house, and the desired
temperature in the house, plus geography, climate, and
latitude of the home site.
Piping/Pump Design Factors
• Flow rate of water to the collectors is affected by the
amount of heat being collected (size of collectors).
• Larger pipes and fittings reduce the pressure drop and
thus pump size, but increase weight and cost of the system.
• The piping must be designed to handle the pressure
and temperature of the fluid inside them.
• Insulate the pump and piping to hold in heat.
• The pump should be sized to produce the required
flow of water and overcome the pressure drop of the
Storage Tank Design Factors
• Storage tank should be designed to handle the
temperature and pressure of the fluid inside it.
• Insulate the outside of the tank to hold in heat.
• Provide a drain line to clean out dirt that builds up in
the bottom of the tank.
• Pressure/temperature relief valve for storage tank and
A solar heating system requires a much more complex
control system than on other residential heating systems
such as heat pumps or gas/oil fired furnaces. The heart
of the control system is a differential thermostat that
measures the difference between the water temperature
in the collectors and the water temperature in the storage
tank. This is so when the water in the collectors is 10 to
20 degrees Fahrenheit above the temperature in the tank,
the pump runs to add warmer water to it. Some controllers
support variable speed pumps which improve the
efficiency of the system by controlling the water flow rate
based on the amount of solar heat present at the collector.
I would like to see a photovoltaic sensor placed on the
solar collectors to modify the speed of the variable speed
pump to capture the maximum amount of solar heat and to
turn the water flow off when the incoming solar irradiation
(insolation) drops below a certain value. Ambient air
temperature sensors could be used to shut down and drain
the outside loop when the temperature approaches the
freezing point. Any outdoor instrumentation and controls
should be weatherproofed. If you use zone control in
which different areas of the residence have their own heat
exchangers or hydronic loops, each of these zones will
need an independent thermostat, fans/controls, and water
Inertial Navigation System Basics
QI have been reading about inertial navigation systems which do not need a radio signal to determine their location. Could you explain these systems?
Colorado Springs, CO
AAn inertial navigation system depends on a method of determining speed and distance moved from a fixed point without the need for external signals such as radio navigation devices
or GPS device use. First, I will look at navigation principles
to make sure everyone is on the same page before moving
on to explain how the inertial navigation systems work.
The purpose of navigation is to get from one point to
another predictably. Figure 3 shows a simple navigation
example with the dashed line representing the path or
course we will take. In Figure 3, our goal is to go from
Point A to Point B which is a seemingly simple process.
To make our navigation problem more useful, we need
to consider the direction from Point A to Point B and the
distance from Point A to Point B as is shown in Figure 4.
QUESTIONS and ANSWERS
Post comments on this article at
n FIGURE 3.
n FIGURE 4.
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