On a good day, our PV panels generate around 10kWh of electrical energy, enough for several hot baths. Sadly, most of that free energy disappears away into the grid and our DHW remains cold. I need a way of routing 'my' precious electricity for my own purposes rather than someone elses.
Switching on the immersion heater during the day is no use because PV-generation is so variable. Power can drop ten-fold in just a few seconds as dense clouds go by. Instead, the load needs to be adjusted dynamically to match the surplus power. The monitoring aspect is well covered at http://openenergymonitor.org
Solid-state controllers are frequently used to reduce the power that is consumed by an appliance by rapidly interrupting the supply. Thats fine when power can only flow in one direction. But when the sun comes out, our mains current can flow in either direction. When power is being drawn from the grid, even momentarily, our energy use is precisely metered and we are charged for it. But for any periods when we generate more that we consume, the surplus energy just disappears off into the grid without even a Thank You. As Baloo might well have observed, " It's gone man, Solid Gone!"
We therefore need a continuously variable 'electronic load' which has similar VI characteristics to a resistive load of the appropriate value. When there is 3kW to spare, it needs to emulate a 20 Ohm resistor; and at 1 kW, 60 Ohms. By putting the electronic load in series with a standard 3kW immersion heater, any rating from 0 3kW can be accommodated. Peak power at the electronic load will be at the half-power point when each load is dissipating 750W.
When operated in its linear mode, a solid-state device dissipates the same amount of energy as if it were a resistor with a similar voltage drop across its terminals. To carry heat energy away from an electronic component, you need a heat-sink, and water-cooled ones work best. An array of solid-state devices operating in linear mode with a large DHW-cooled heat-sink should do the trick.
Is anyone else thinking along these lines? There must be thousands of PV owners out there who would just love to have a system like this
Switching on the immersion heater during the day is no use because PV-generation is so variable. Power can drop ten-fold in just a few seconds as dense clouds go by. Instead, the load needs to be adjusted dynamically to match the surplus power. The monitoring aspect is well covered at http://openenergymonitor.org
Solid-state controllers are frequently used to reduce the power that is consumed by an appliance by rapidly interrupting the supply. Thats fine when power can only flow in one direction. But when the sun comes out, our mains current can flow in either direction. When power is being drawn from the grid, even momentarily, our energy use is precisely metered and we are charged for it. But for any periods when we generate more that we consume, the surplus energy just disappears off into the grid without even a Thank You. As Baloo might well have observed, " It's gone man, Solid Gone!"
We therefore need a continuously variable 'electronic load' which has similar VI characteristics to a resistive load of the appropriate value. When there is 3kW to spare, it needs to emulate a 20 Ohm resistor; and at 1 kW, 60 Ohms. By putting the electronic load in series with a standard 3kW immersion heater, any rating from 0 3kW can be accommodated. Peak power at the electronic load will be at the half-power point when each load is dissipating 750W.
When operated in its linear mode, a solid-state device dissipates the same amount of energy as if it were a resistor with a similar voltage drop across its terminals. To carry heat energy away from an electronic component, you need a heat-sink, and water-cooled ones work best. An array of solid-state devices operating in linear mode with a large DHW-cooled heat-sink should do the trick.
Is anyone else thinking along these lines? There must be thousands of PV owners out there who would just love to have a system like this