Stage
1: A Simple Inverter/Battery Set Up
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The arrangement shown was used
to carry out the initial feasibility study. The system was
used to power the garage, side passage, utility room and
outside toilet lights. The load consisted of 2 * 22W Bulbs
controlled by a PIR, 2 individually switched 36W Neons plus
a pair of 50W halogen lights. All the items apart from the
PIR are relatively low usage and were chosen because they
were not particularly important and are easy to get to for
wiring. The results obtained plus assumptions and comments
are shown below. |
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Caution: Electricity can be dangerous.
Modifications to any electrical apparatus or wiring should
only be carried out by a competent person.
It is
important the inverter neutral is isolated from mains neutral
otherwise there will be around 800V between mains live and inverter
live due to the voltages being out of phase. The inverter must
be properly connected to mains earth.
Inverter |
Average
Time On
(Hrs Daily) |
Inverter
Input
(Amps) |
Inverter
Input
(Watts) |
Inverter
Output
(Watts) |
Inverter
Efficiency |
No Load |
0 |
0.30 |
3.6 |
0 |
0.0% |
PIR/Light Detector |
24 |
0.24 |
2.9 |
2 |
30.9% |
36W Neon |
2 |
3.78 |
45.4 |
38 |
77.6 |
2 * 36W Neon |
0.1 |
6.51 |
78.1 |
74 |
90.6 |
2 * 11W Lo Energy |
0.3 |
2.26 |
27.1 |
24 |
78.1 |
2 * 50W Halogen |
0.5 |
8.58 |
103 |
100 |
93.8 |
Charger |
Time
Switch
(Watts) |
Charger
Input
(Watts) |
Charger
Current
(Amps) |
Charger
Output
(Watts) |
Charger
Efficiency
(%) |
Battery
Input
(KWHr/day) |
Total
Power
(KWHr/day) |
On 4.3 Hrs/day (Cheap Rate) |
24.0 |
119.0 |
6.4 |
76.5 |
64.3 |
0.510 |
0.312 |
System Efficiency |
System
Input
(KWHr/day) |
Power
Supplied
(KWHr/day) |
Overall
Efficiency
(%) |
Totals |
0.510 |
0.187 |
36.8 |
Cost Comparison |
Cheap
Rate
(p/KWHr) |
Normal
Rate
(p/KWHr) |
Cheap
Rate
(KWHr/day)
|
Normal
Rate
(KWHr/day) |
Cost
(per Day) |
Cost
(per Qtr) |
Original |
4.40 |
10.50 |
0.012 |
0.175 |
£0.019 |
£1.71 |
Inverter System |
4.40 |
10.50 |
0.510 |
0.0 |
£0.022 |
£2.02 |
Assumptions
1. Inverter system uses only cheap rate electricity.
2. Originally items used only on normal rate electricity.
3. Assumes battery energy conversion 100%.
4. Assumes stable battery voltage of 12V which it isn't but the variations should
average out.
5. Usage averaged over whole year for simplicity.
6. The time switch consumption of 1W has been added to the battery charger input
power.
7. Battery charger reverse leakage current of 70mA included in inverter
input current and power figures.
Comments
1. Efficiency is very low.
2. Time Switch on time has to be adjusted to suit load - probably
fairly regularly.
3. Battery charger efficiency is lower than expected.
4. Cost using this setup is slightly more expensive than without
it.
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