|
Another view on solar
Commentary by Michael Vickerman
Talking about solar power seems to have a polarizing effect on
us. Some people look at the solar path as
representing a potential escape route from the emerging
fossil fuel crunch. Others believe solar (at least PV) is a
net energy loser that cannot deliver on the promises that
proponents make. Allow me to offer a more nuanced
perspective.
There is no doubt that the sun is an underused and
underappreciated energy resource. Solar energy has the
potential to diminish a building's heating, cooling and
electrical requirements to a fraction of what is currently
the norm. Through a combination of orientation, design,
different materials, and understanding of the building as an
energy system, one can use solar energy to displace much of
the conventional energy that is typically imported to
illuminate interiors, maintain a comfortable temperature
range, and run appliances. Solar may not be a concentrated
resource, but it is versatile; it can provide heating and
cooling, light, and electricity. You can even cook with it.
Certain applications of solar (daylighting, passive solar,
solar water heating) have a high net energy return.
Generating electricity from sunlight, on the other hand, has
a much lower net energy return. Installation-specific
details can make a big difference in this regard, an example
being whether it defers a distribution upgrade like a line
extension or a bigger transformer.
Even with a low net energy balance, PV can contribute to a
very efficient, low-input building if it's combined with
other solar, renewable, and energy-efficient features.
Recently, I toured a new law office building in eastern
Wisconsin (Ritger Law office in Random Lake) that sets a
very high standard for sustainable energy design. The
structure combines daylighting design principles (reducing
the building's connected load), a ground-source heat pump
for heating and cooling, radiant floor heating (first floor
only), operable windows, and 5 kW of UniSolar amorphous thin
film solar panels adhering to a standing seam roof. Most of
the PV power feeds directly into the grid through a net
metering arrangement, but some of it is routed into an
uninterruptible power system (UPS), with battery storage
providing continuous power to selected critical loads.
Usually, UniSolar sends PV material to a fabricating center
in Tijuana where it is applied to the roofing material, but
in this case, the PV material was shipped directly to the
law office and applied to the roof on-site. Eliminating this
intermediate step must have raised the net energy balance of
this PV system, one would think.
There is no other building in Wisconsin that so completely
and adeptly captures solar energy as this one. But, with one
exception, all of the benefits from employing and
integrating these sustainable features stays with that
building. They aren't transferable to other locations. The
natural illumination coming through the light pipes cannot
be transmitted through the wires into another building. Same
story for the cooling breezes blowing through the open
windows. The law office's UPS doesn't help the building
across the street when the grid fails. Only the PV-generated
electricity supplying the grid results in a system benefit.
As a result of the building owner's creativity, the
non-electric solar features are in effect subsidizing the PV
installation, creating the energy savings that make it
affordable to this owner. Configuring the PV system so that
the law office can still operate in the event of grid
failure also adds value to the building, which the owner
derives full benefit from. Would this individual have been
able to afford the high cost and low net energy return of a
stand-alone PV system without the other building-specific
solar and energy efficiency features? Very doubtful.
Unless governmental units start throwing unprecedented
levels money at PV, installations on commercial buildings
will largely be confined to instances like the above, where
business owners figure out a way of subsidizing it through
other sustainable energy features. (This does not apply to
businesses that earn more money than they know what to do
with.) It takes clever and committed people to go through
the process of customizing a building for that purpose, and
to succeed at it. By my reckoning, they are as rare as they
are outside the mainstream. Because they exist in such small
numbers, they do not constitute a market force that can
leverage lower unit prices. If market pull were left only to
these individuals, PV system prices, which have not dropped
significantly in recent years despite government predictions
to the contrary, will continue to be a considerable barrier
for most people.
Along comes the city of San Francisco, which has a most
unusual bond issue on the ballot this November. If approved,
San Francisco's ballot initiative would create $100 million
in bonding authority for the purpose of acquiring and
installing PV systems. I don't believe a major outlay for PV
has ever been subjected to the will of the voters until now.
All indications thus far point to easy passage.
Assuming no surprises this November, San Francisco stands to
be the first government in the Lower 48 to adopt a fully
taxpayer-supported PV initiative. This is a huge departure
from traditional incentive programs, which are designed to
leverage other people's money through buydowns or long-term
financing.
This approach should result in lower-cost PV modules, as the
city can exert considerable market power in negotiating
purchase terms with suppliers. It might even attract a
commitment from a PV manufacturer to site a new facility in
or near the city.
However admirable San Francisco's commitment to
mainstreaming PV may be, one wonders if it will have any
measurable effect on the city's energy profile. Will the
development pattern be to place arrays on the rooftops of
big box retailers and other flat-roofed commercial
structures, in an effort to hold down installation costs? If
so, will there be a coordinated effort to reduce connected
load within the host structures? If not, then a particular
rich source of energy savings will go untapped, and the
city's taxpayers will be all the poorer for it.
Commercial real estate development is a major source of
America's energy profligacy. In an effort to drive down
first costs, contractors have settled on formula approaches
that assume no responsibility for energy performance beyond
code compliance. The result is a depressing stream of
underdesigned, overengineered structures that resemble, for
intents and purposes, air-conditioned ovens. Whether a
building is located in Anchorage or Atlanta, it will pretty
much have the same engineering specifications for rejecting
the ambient climate. Because it takes much more energy to
keep the local climate out rather than to let it provide
some or all of the heating, cooling, illumination, et
cetera, a PV array on the roof of a commercial building
isn't likely to make much of a dent in its energy
requirements. But if the possibility of PV on the building
prompts an architect and building owner to come up with a
new design for beating the energy code by, say, 20%, then
the PV option should get some of the energy credit for that,
no?
What I'm getting at is that knowing the generic net energy
return of an individual energy resource tells us little
about how it relates to other energy resources, and how it
might function in a customized installation. In the case of
PV, its value as a stand-alone energy system may be limited,
but, when it becomes the driver for a building-wide package
of conservation and sustainable energy measures, PV can
engender far more impressive results than what could be
accomplished through traditional linear thinking.
Michael Vickerman is executive director of RENEW Wisconsin
|
|
