GB2499474A

GB2499474A - Router to divert excess solar generated electricity to an immersion heater

Info

Publication number: GB2499474A
Application number: GB1212314.7A
Authority: GB
Inventors: Michael Joseph Clifton
Original assignee: Individual
Current assignee: Individual
Priority date: 2012-02-14
Filing date: 2012-07-10
Publication date: 2013-08-21
Also published as: GB201202491D0; GB201212314D0

Abstract

A router diverts electricity generated by a variable source such as from solar radiation using photo voltaic cells or wind force using a turbine to a load 8 such as an immersion heater only when sufficient solar power is available. A power monitor 6 measures the power from a supply or grid; compares it with the solar power and inhibits load 8 turning on until its demand can be met by the variable source. The immersion heater can also be turned on manually or by a time switch 9. Power can be monitored and compared using current transformers 4, 6 and whose output voltages and phase are added using resistors (fig 3, R1-R4) and used to trigger a triac (fig 3, S1) when of sufficient magnitude, to make power either fully or partially available to load 8.

Description

SOLAR/SELF GENERATED POWER ROUTER.

Electricity is produced from solar radiation using arrays of photo voltaic cells or from wind force using wind turbines. The power output from solar panels varies with the intensity of solar radiation and the shading of the solar cells. Where the solar generated power is fed into a national electrical grid system the generator is normally paid for the power produced and is also allowed to freely use the power produced for his own purposes. Thus he will receive free electricity provided his electrical load is less or equal to that being produced from his solar source, otherwise some or all of his power usage will come from the electricity grid and would have to be paid for.

He could of course switch all or part of his load off manually when his solar power source reduces in output but this would be impractical as solar radiation will vary throughout the day. A typical solar power system, augmenting a consumer's normal connection to a commercial or national supply grid, is shown in Fig.l. The solar power source is converted to AC and synchronised with the normal AC power source. It is then connected in parallel with that normal power source, via meter 1 which measures the power generated, enabling the generated power to feed the loads via the consumer unit 2 and to feed into the normal supply via its supply meter 3. It would be beneficial if any non time critical heavy load e.g. an immersion heater 8 could be switched on only when solar power is available and via a time switch 9 during any period when power is available at reduced rates from the commercial source. With a constant load of say 3kw the router can supply 100% of the load if the solar output is sufficient and proportionately less in lower solar input

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conditions. The router efficiency is better than 99%, at full load, and therefore does not have a significant insertion loss. The router unit circuit comprises 4 basic blocks as shown in Fig.2; a circuit 4 which measures the current output from the solar system, a circuit 6 which measures current to or from the grid, a circuit 7 which, using resistors R1 to R4, compares (adds) the secondary voltages and phases of Trl and Tr2, the result of which, when of sufficient magnitude, will trigger circuit 5. a triac SI, making power available to the load connected to the router when sufficient power is being generated.

The router circuit is shown in Fig. 3, it utilises suitable current transformers Tri 8c Tr2, these effectively measure power (Vl is constant therefore current I is proportional to power). When sufficient solar current (Is) is generated Si will partially or fully switch on. Any surplus current (Ig+) will feed other loads on the consumer unit 2, or feed into the supply via Tn, reinforcing the gate voltage of Si. If current flows from the supply grid to the consumer unit (Ig-), Tr2 reverses the phase of its secondary voltage, which is added to the voltage from Tri. This anti phase feedback switches Si off, maintaining this situation until Ig reverses direction. The choice of current transformer ratios and values of Ri, R2 and burden resistors R3 and R4 determine the on and off points of Si and can be set to allow Si to switch at any desired level of solar current Is. An alternative connection for Tr and Tr2 10 is shown in Fig.3.

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Drawings References

Figure 1. Typical solar power connection.

Figure 2. Solar Power Router block diagram. Figure 3. Solar Power Router Circuit.

Reference Numbers:-

1. Solar power meter,

2. Consumer unit with multiple circuit breakers.

3. Supply meter.

4. Solar power sensor.

5. Power control circuit.

6. Grid power input/output sensor.

7. Comparator circuit.

8 . Immersion heater with thermostat.

9. Optional time switch.

10.Alternative circuit for Tri & Tr2.

Tri & Tr2 Current transformers

Si Triac

Rl, R2, R3, R4 Resistors

Is Solar generated alternating current. Ig Alternating current to or from grid.

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Claims

1. In order to maximise the benefit of producing free electrical power, albeit from a source with a variable output, for example to heat water using an immersion heater, a router circuit is produced which monitors the power available from the solar source and makes that power available for directed use.

2. In circumstances where other loads are switched on and could therefore divert this free power from the router's load, thus making it consume power which must be paid for, two further circuits are utilised, a power monitor 6 which measures the power or current being delivered from the supply or grid, this current is then compared with the solar power or current available by circuit 7, the comparator then inhibits the router from switching its load on until it's demand can be met from the solar source.

3. The use of current transformers to simply compare, control and route the use of solar generated power provides significant cost savings.

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4. The circuit functions described in claims 1. and 2. are fairly simple and can be housed in an enclosure and be mounted near to the consumer unit or could be built into a purpose designed consumer unit.

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4. The circuit functions described in claims 1. and 2. are fairly simple and can be housed in an enclosure and be mounted near to the consumer unit or could be built into a purpose designed consumer unit

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> S- AMENDMENTS TO CLAIMS HAVE BEEN FILED AS FOLLOWS

Claims

3. The use of current transformers to simply compare, control and route the use of solar generated power provides significant cost savings both in the object of saving on purchased power and in the hardware used to achieve this, whereby a simple analogue circuit produces a significant proportion of the savings made by other known methods which use more costly and sophisticated digital and radio frequency techniques to achieve a similar end.