Saturday, 1 February 2020

Heat Data Confirms Battery Energy Conversion > 100%


Background
Previous tests provided results using measurements of duration, battery terminal voltage, and load resistances.  Those results indicated that the total initial energy stored in the test circuit's rechargeable battery could be effectively 'recycled' by feeding a proportion of the input energy back to the battery from temporary storage within the circuit

Energy-to-work conversion ratios in the range 170-200% were observed

The circuit operates with all the usual inefficiencies but the duration of its operation becomes extended due to the real-time recharging of its supply battery


Thermal Profile testing
These latest tests confirm the ability to recycle some of the original energy, by measuring the thermal activity of the total system:
 -  the reference test measures the temperature at the load resistor, against time, when all the input energy is dissipated directly within the circuit (results labelled as 'No F/b');
 - the active test measures the temperature at the load resistor, against time, for the arrangement where some energy is used to partially recharge the supply battery (results labelled as 'With F/b')

The temperature of the load resistor is related to the current it carries - the value of the heat energy dissipated by the resistor is given by the product of the resistance with the square of the current and with time

The circuit has been arranged in such a way that the total supply current for the circuit is the same for both the reference test and the active test.  If the results show that the same temperature is achieved at the load resistor for the duration of both tests, then the comparative duration values will indicate whether or not the circuit arrangement with energy feedback to the battery (See Fig. 1) can effectively operate for longer (ie. produce more work) than the circuit which just dissipates all the energy supplied from the battery into the circuit in one pass
Fig. 1 - Ringwood Energy Recycler Block Diagram



Test procedure
The circuit has been simplified and re-arranged to provide for measurement of temperature on a single 27 ohm load resistor which is in the input path of the total current supplied to the circuit (See Fig 2.). The supply battery voltage has been increased to 5.2V (nominal) in order to improve the significance of the temperature rise compared with the ambient.  The temperature values, deltaT, presented on the graph represent the difference between the temperature probe, monitoring the load, and the sensor monitoring the ambient temperature

The circuit is tested in two configurations:
  1. (Reference test) the output pulse from the BAT42 diode is connected to the cathode of a 5v1 zener diode, to dissipate the pulse energy within the circuit;
  2. (Active test) the output pulse from the BAT42 diode is connected to the +ve terminal of the battery, where it provides a partial recharge with the pulse energy

The switch S1 shown in Fig 2. provides these 2 test arrangements, a) and b)

Fig. 2 - Test circuit used to obtain thermal output profile

The circuit and battery are completely enclosed within a metal container, which is lined with a layer of heat-insulation.  A thermistor temperature probe is fixed to the 27 ohm load resistor;
A second thermistor sensor records ambient temperature (within the datalogger interface)


Results
The numerical results, obtained from the data spreadsheet calculations, show that for a full discharge of energy from the battery in each case:-
  1. (Reference test)
sustained an average deltaT of 9.92 degC for a total of 8.4 hours
  1. (Active test)
sustained an average deltaT of 9.98 degC for a total of 10.6 hours

(The test durations are measured between mid-point values of the rising and falling edges of each temperature profile; the temperature profile for each test has been aligned then at the selected point for that test, to provide a direct comparison of their respective durations)

These results are presented graphically in Fig 3:

Fig. 3 - Thermal Output Profile results

A separate discharge test of the same battery, using a 68 ohm resistor, produced a value of 10650 Joules for the total energy stored by the battery when fully charged;  using this value, the average current drawn by both the reference and the active test circuits is calculated to be approx 70mA


Conclusions
The results confirm that both the reference test and the active test are operating with the same average supply current, as evidenced by close agreement of the average temperatures measured at the load resistor in the supply path

Since the active test duration is longer than the duration of the reference test, the circuit with feedback of energy to its supply battery is shown to have increased the total amount of work converted from that battery by a factor of  (10.6 / 8.4) = 1.26

These results confirm the results of previous testing (mentioned above);  the initial energy obtained and converted from the battery (10650 Joules) and temporarily stored within particular circuit components can then be used to partially recharge the supply battery in real-time and extend the total amount of work which is converted by the whole system (13450 Joules)

The example arrangement tested here effectively extended the total amount of work converted from the supply battery to 126%

Thursday, 29 November 2018

Observing a 170% conversion of battery energy into work

The basis of the Ringwood Energy Recycler circuit used in these tests is not particularly unusual - it's a simple blocking oscillator and it has a work-efficiency of approximately 85% (quantifiable-work performed for total energy supplied)


Fig. 1 - Circuit with current feedback to supply battery


Unquantified losses include resistive heat-loss in the switching transistor & diode, coil windings, and transistor biasing


The switching circuit operates at approx 67 kHz, in 2 half-cycles: a `Drain` step, followed by a `Recharge` step

Fig. 2 - Current paths in the system


The battery capacity can be characterised by discharging it using a resistor with a known value, over the terminal-voltage range 4.2V to 3.45V


Using a battery with 3 NiMH cells of 750mAh rated capacity, a fully charged battery supplied a 268 ohm (measured) resistor with an average power of 14.4mA x 3.86V for 42.5 hours, converting a total of 8504 Joules of energy


When the discharge resistor is replaced with the preliminary circuit (ie. the feedback diode is connected to a spare battery which is not the supply battery, but similar construction) the quantifiable work consists of two parts:- 
 - converting 3105 Joules to illuminate some LEDs
 - recharging the spare battery by using 4238 Joules of energy which is being temporarily stored in the circuit as a by-product of the oscillator operation

The circuit provides this quantifiable work for a total of 30.5 hours, drawing an average of 20.1mA at 3.86V to draw a total of 8603 Joules (approximately matching the total energy, 8504 Joules, converted by the nominal 270 ohm resistor)

In this mode, the circuit draws the total energy available and converts this to 7343 Joules of quantifiable work, giving a quantifiable-work efficiency of 85%


When the feedback diode is re-connected to the supply mode (see Fig. 1), the circuit will operate for almost twice the duration of the conventional, non-feedback mode - the circuit now operates for a total of 60.5 hours, whilst drawing the same real average power, 20.1mA at 3.86V,  (compared to 30.5 hours duration for the non-feedback mode) with the loads remaining the same values

[The circuit can operate at the same power drain for longer because it is constantly re-charging its supply with a proportion of the energy which has been input - the actual supply current drained is pulsed, with an average of 20.1mA, whilst 10mA av. is recharged back into the battery, being interleaved each cycle similar to time-division-multiplexed operation (see Figs. 2 & 3), resulting in a 'virtual' current drain from the battery of (20.1mA - 10mA) = 10.1mA av.]

Fig. 3 -  Bipolar current pulses in supply connection (blue trace)


The total energy drawn by the circuit is now 16898 Joules

The efficiency of the oscillator circuit compared to its total energy drawn hasn't changed essentially:
 the quantifiable work has increased to 14566 Joules, and these values give an efficiency of 14566 / 16898 = 86%

The overall system efficiency for quantifiable work from the original energy in the battery, however, is now 14566 / 8504 = 170%

The total system efficiency for conversion of energy in the whole system (battery + circuit) now becomes: 16898  / 8504 = 199%


The system is recycling its input energy by a factor of 1.99

The 'feedback to supply' mode has extended the duration for circuit operation and enabled the amount of useful energy available for the LEDs to be approximately doubled compared to the 'no feedback' arrangement

Although the total work converted by the switching circuit LEDs, on their own, remains less than the original supply of energy, and the energy converted by those circuit LEDs matches that of a passive resistor-driven LED arrangement (6159J vs. 6169J), the 'With-Feedback' current arrangement still enables the circuit to produce a level of light output slightly greater than the passive DC-drive arrangement (146 Ft-candles vs 140 approx.) but for approximately 34% longer duration (60.5 hours vs. 45 hours)

This resulting system behaviour provides a worthwhile gain, which has been enabled by the 200% conversion to system work (16898J) of the original store of energy in the battery (8504J)
Fig. 4 - Blue trace: Battery discharge profile (No energy feedback);
Red trace: LED drive level (DC volts)




Fig. 5 - Blue trace: Battery discharge profile (With energy feedback);
Red trace: LED drive level (DC volts)

Sunday, 13 March 2011

Charge Anomaly confirmed


Conclusions:
The results below, from the switched-charge experiment (
12 May 2008), show that the total value of charge-separation in the isolated test circuit increased by approximately 25% from the initial state of the circuit, after the switched transfer of charge from the input capacitor to the output capacitor

0.299 Coulombs of charge-separation were removed from the input capacitor, C1  


0.913 Coulombs of charge-separation were added to the output capacitor, C3


(any charge on the only other two capacitors in the circuit - 500uF and 0.1uF - was small enough to ignore by comparison with that on C1 & C3)

 the final state of charge in the circuit was significantly different from that expected by conventional circuit analysis - the circuit had gained an anomalous excess of charge-separation!




Charge Results:
Input cap, C1: 0.299F
Start volts: 8.0V
Start charge: 2.392Coulombs

Final volts: 7.0V
Final charge: 2.093C

Output cap, C3: 0.342F
Output volts: 2.67V
Output charge: 0.913C


charge switched from input to output capacitor, then discharged by S2

Total start charge: 2.392C
Total end charge: 2.093 + 0.913 = 3.006C


(ignoring charge on switching cap, C2, 500uF)


Switched-charge test period: 45.8s
cycle period: 0.85ms
charge period: 0.17ms
charge/cycle duty: 0.17/0.85 = 20%



Stand-alone switched-charge experiment setup:-
(12 May 2008 )


Purpose:
the circuit was constructed to transfer charge from an input capacitor to an output capacitor, via a switching capacitor and inductor, using a number of repeated cycles to switch a small amount of charge in each cycle

the switching was achieved using MOSFET devices driven by a free-running oscillator constructed using NAND gates from a CMOS logic device

the entire circuit was powered solely by the initial charge in the input capacitor

the only external connection was to a DVM, used to monitor the voltage on the input capacitor

the test achieved the same results, regardless of whether the DVM was connected for the full duration of the test or if it was disconnected at the start and only reconnected a few seconds before the end

Method:
Open switch S1, close switch S2;
Monitor C1 volts with DVM;
Charge C1 to approx 9V;
When C1 voltage approaches 8V then open S2;
As Voltage on C1 measures 8V, start timer &
  Close S1, to connect C1 into circuit;
When voltage on C1 reaches 7V, stop timer &
open S1;
  measure voltage on C3 with DVM;


Switched-charge experiment schematic

Parts list:
R1: 12K 0.25W
R2: 100K 0.25W variable
R3: 100K 0.25W variable
C1: 0.299F (4x1F, 2.3V series)
C2: 500uF 16V
C3: 0.342F (4x1F, 2.3V series)
C4: 0.1uF ceramic
D1: OA93
D2: 1N914
D3: 1N914
Q1: FDN304P
Q2: IRF540N
L1: 2.5mH
U1-U4: 4093B Quad Schmitt NAND