Page 38 - EE Times Europe Magazine – November 2023

38 EE|Times EUROPE

GREENER ELECTRONICS | ENERGY HARVESTING
Ambient Light Harvesting Heads Indoors

By Robert Huntley

arvesting energy from the sun using photovoltaic panels is a decades- PRINTED AND CUSTOMIZABLE PV CELLS
old method that underpins our society’s switch to renewable energy OPTIMIZED FOR INDOORS
The two companies take slightly differ-
sources. Vast farms of solar PV panels are fixtures of the landscape in ent approaches to delivering their PV cell
Hmany countries, and on a smaller scale, compact PV cells are used in technologies. Lightricity’s technology was
consumer, commercial and industrial products ranging from patio lights to initially developed by Sharp Laboratories in
2012 before being commercialized with the
calculators and smartwatches to battery-less embedded IoT sensors. formation of Lightricity in 2017. The company
claims its harvesting technology, based on
PV cells have proven to be an effective most cases, you don’t have control over the a proprietary process, can deliver 6× the
method of harvesting energy from the sun environment.” energy output (20 µW/cm ) of existing PV
2
during daylight hours. The cells’ spectral Kauer explained that in an office, a device cell methods (typically 3–5 µW/cm ), such as
2
response is optimal when they are exposed to could be deployed under a desk or in an amorphous silicon and organic PV measured
sunlight, but historically, they have performed electronic label at the bottom of a shelf, at 200 lux.
poorly in indoor light. so harvesting down to 50 lux is an ideal Lightricity’s PV cells are available in sizes
Today, however, considerable R&D activity requirement. from <1 cm to 2 cm and thicknesses from
2
2
is yielding a new breed of PV cells designed Brice Cruchon, CEO of Dracula 0.65 mm to 1.5 mm. They are constructed
to harvest energy from low-level artificial Technologies (Valence, France), described the from a proprietary material that the com-
light sources indoors. EE Times Europe spoke light levels a user might typically encounter: pany says is highly temperature-stable from
to Dracula Technologies and Lightricity, two “If you take a lux meter around an indoor –40°C to 200°C, and they can be mounted on
innovators of PV cells optimized for use in environment, it will measure between 30 lux semi-flexible and flexible PCBs to conform
artificial and indoor-light environments. and thousands of lux. In an office, it’s around with nonplanar surfaces. The PV cells can be
400 lux to 500 lux. In the corners, you might assembled on a PCB together with all other
HARVESTING SUSTAINABLE ENERGY FOR measure from 30 lux to 60 lux, and you can components in a standard SMT reflow manu-
INDOOR DEVICES reach 5,000 lux or more close to the light facturing process.
“What the world needs now is to expand source. In an industrial building, the levels Dracula Technologies’ novel approach
the scope of energy harvesting” by tapping might go up to 2,000 lux to 3,000 lux. In most yields printed and flexible organic PV cells.
indoor ambient light sources, said Matthias cases, the real values compatible with an IoT Photovoltaic ink is printed onto a flexible,
Kauer, CEO and co-founder of Lightricity sensor are between 50 lux and 400 lux. lightweight substrate and then encapsulated
(Oxford, U.K.). “We have this proliferation “What’s really important is that the with a plastic film to protect it from the
of battery-powered devices for industrial harvesting technology is efficient across the environment. The company says that its Layer
automation, building automation, etc. They range,” he added. “If you go to low- technology (Figure 1) is stable for up to
require a solar cell with high efficiency at luminosity levels below 200 lux, you’ll see 10 years indoors. The cell is bifacial, allow-
all light levels, down to very low light levels. that only two or three technologies can pro- ing it to harvest energy from both sides if
The thing with light harvesting is that, in vide high performance.” mounted accordingly.

Figure 1: Dracula Technologies’ Layer printed organic PV cell (Source: Dracula Technologies)

NOVEMBER 2023 | www.eetimes.eu