Tech Briefs Magazine - June 2024 - 20

Simulating Heat Systems
make it out of dirt. " Polar Night Energy's
system faces the same core challenges as
any other energy infrastructure. It must
deliver power to people when they need
it, where they need it, and at a manageable
price. This means that storing and
distributing energy is as important as its
generation. Existing infrastructure
meets these challenges in familiar ways.
For combustion-based heating, fuels
Figure 2. Markku Ylönen with a representative sample of Polar Night Energy's dirt-cheap heat storage
medium. (Image: PNE)
like oil and gas are stored and moved to
where they can be burned. The electrical
grid also supports the efficient distribution
of power and makes use of energy
generated through renewable means
like wind and solar. The intermittent nature
of daylight and strong winds, however,
is a stubborn problem. Energy storage
is needed to maintain steady power
output throughout the peaks and valleys
of renewable inputs. But even with recent
advances in battery technology,
storing electric power remains relatively
expensive, especially at the scale required
for heating buildings. What if,
rather than storing electricity, a " battery "
could store heat instead?
Many conventional heating systems already
store and distribute heat by retaining
and circulating warm water. Eronen
and Ylönen recognized the benefits of
water-based heat storage as well as its limitations.
" There is only so much heat you
can add to water before it becomes
steam, " said Eronen. " Steam can efficiently
distribute heat, but it is not really
cost-effective for large-scale storage. " To
avoid the drawbacks of storing heat in
water, they instead turned to sand - 42
tons of it (Figure 2).
Figure 3. Eronen (foreground) and Ylönen inspecting the ductwork of a Polar Night Energy heat
storage vessel. (Image: PNE)
The hot air then flows back out of the
vessel into a heat exchanger, where it
heats water that is then circulated
through building heating systems. The
sand's heat storage capacity ensures
that even when the resistive elements
are cool, the circulating air is still hot
enough to keep the water (and buildings)
warm.
20
" We only have pipes, valves, a fan, and
an electric heating element. There is
nothing special here! " Eronen said.
A Battery for Heat Made from
Sand
Notable chemical engineer Donald
Sadoway is quoted as saying: " If you want
to make a dirt-cheap battery, you have to
www.techbriefs.com
After the Sun goes down, the sand's
stored heat is gradually released back into
the circulating airflow. This keeps the air
hot enough to maintain steady temperatures
in the water that flows through customers'
radiators. In this way, sand enables
solar power to keep people warm,
even during the darkest and coldest Finnish
nights. " Sand provides four times the
energy storage capacity of water, " Eronen
said. " Sand is efficient, nontoxic, portable,
and cheap! "
The Sophisticated Analysis
Behind a Simple Solution
Cost efficiency is the foundation of Polar
Night Energy's value proposition. " As
soon as we decided to pursue this idea,
we were trying to figure out how the finances
looked, " said Eronen. In their
quest to do more with less, Polar Night
Energy has long depended on numerical
Tech Briefs, June 2024

http://www.techbriefs.com

Tech Briefs Magazine - June 2024

Table of Contents for the Digital Edition of Tech Briefs Magazine - June 2024