IEEE Electrification Magazine - March 2018 - 24

research shows the possibility of ultraefficient solar-H 2
conversion system.

The Disadvantages of PV-EC
Systems Without Converters
the conventional PV-ec systems without converters have
clear disadvantages, e.g., they are best-performed with
specific light conditions. If the light density varies, as the
real sunlight intensity changes every hour, the I-V characteristics of a PV varies, so it is difficult to predict and optimize the best performing condition. For practical
utilization, the PV-ec system should be flexible regardless
of sunlight. to maximize PPV,max and to keep track of the
intensity of sunlight, there is no reason to postpone the
power converting technique. therefore, the dc-dc convert-

er can provide the mPPt technique to follow the maximum power of solar light.
there are several related reports on utilizing converted
technology for solar light H 2 conversion. the garrigos
group suggested the insulating-type topology of the converter to scale up the PV-ec system, which is caused by
high voltage generated from the PV. the same group proposed the topology to precisely regulate the output current
control region, as shown in Figure 4(a). this situation only
occurs when the ec needs more voltage than the VPV,max,
which requires delicate duty control. With the Agbossou
group, the design principle of a converter covered the
whole H 2 generation and the H 2 storage system.
the nam and ha group reported the casual relation
between the converter on/off ratio, the duty and final

Output Capacitor
EC
Error
Amplifiers

4-20 mA and
Telemetry

Converter

Input Capacitor
PV

(a)

(b)

Figure 4. The various analyses of a converter-assisted PV-EC system. (a) The topology of the converter for output current control when the
EC cannot properly manage the power from a PV (Garrigós et al. 2014). (Photo courtesy of Elsevier.) (b) A converter efficiency measurement
system based on the ratio between input and output electrical power (Chang et al. 2017). (Photo courtesy of the American Chemical Society.)
uC: microcontroller.

Technion
NREL

Fraunhofer U. Tokyo

NREL

EPFL
Uppsala

U. Hawaii NREL

Caltech

EPFL, STH 12.3%
U. Osaka, STH 2.93%
SNU,
STH
20.6%
0.8
Technion, STH 18.3%
U. Tokyo, STH 24.4%
SNU, STH 19.5%
Caltech, STH 10%
0.6
0.4

MIT

Texas A&M

1.0

U. Tokyo
U. Monash
SNU
SNU

Tandem PV
Single-Junction PV

PH2/PPV,max

Reported STH Efficiency (%)

UC Berkeley

0.2

U. Osaka
1985

1990

1995

2000
Year

2005

(a)

2010

2015

10
20
30
40
AEC/APV at 100 mW cm-2

(b)

Figure 5. The reported efficiency of a PV-EC system: (a) the reported STH efficiency of a PV-EC system by year and (b) the PH2 /PPV,max (produced
H2 energy compared to the solar-driven maximum electrical power) value based on a surface-area ratio between EC and PV. A high PH2 /PPV,max with
a low A EC /A PV indicates an economical PV-EC configuration. EPFL: École Polytechnique Fédérale de Lausanne; NREL: National Renewable
Research Laboratory; SNU: Seoul National University.

I EEE E l e c t r i f i c a t i on M a gaz ine / march 2018

Table of Contents for the Digital Edition of IEEE Electrification Magazine - March 2018