Alternate energy and conservation: sense and nonsense (100+ lines)

Oct 8 00:08 UTC 2002

With alternate energy as everything else, there are some schemes
which work with the equipment we have available, some schemes which
require equipment we don't have yet, and some schemes which won't
work at all.  Appreciating the difference is key to making best use
of what we've got.

Taking some quotes from Fall Agora item 8:

# If Detroit Edison can be persuaded to pay people with panels the
# same on-peak summer rates that they pay other suppliers, solar
# energy in Michigan may be less cost-prohibitive.  Right now it
# runs about 25 cents/kWh because you can only sell it for one third
# what you pay for it, instead of the three times what you pay during
# mid-day in the summer, when you generate the most power and
# when people who don't know any better run air conditioners.

There are two misconceptions in this paragraph.  The first and smallest
is that solar panels produce the most power in the summer.  This is
actually false; silicon PV panels lose capacity with increasing
temperature, and actually put out the most power on sunny winter days.
The reflection from snow on the ground can put more sunlight on a solar
panel than it gets during the summer, adding a double-whammy.

The bigger misconception appears to be that "people who don't know
better" run air conditioners on hot days.  People don't buy air
conditioners for chilly days!  This is a wealthy country, and people
are not going to accept being hot and sweaty in homes and businesses
just to be ecologically correct.  They are going to buy comfort.
The goal of "green engineering" should be to provide it with the
minimum of environmental impact and a reasonable cost.
 
# I'd like the new school building (assuming the bond is approved) to
# include solar panels for co-generation.  If some of the heating can
# also be used to generate electricity, I'd like it to use that, too.

There's an error of nomenclature hiding a misunderstanding, and a
broader question of purpose left hanging here.  Co-generation is
applied to operations which use fuel (such as making steam) where
the process is changed to generate electricity or other useful work
as a byproduct.  For instance, instead of boiling water at atmospheric
pressure for steam heat, a co-generation system will boil water at
high pressure and run it through a turbine to co-generate electricity;
the turbine's low-pressure exhaust steam can be used for space heat.
The net efficiency of co-generation can be very high.

The broader question of purpose involves the  use of solar panels (I
assume that photovoltaic panels were meant here).  PV is some of the
most expensive conversion hardware on the market, and is really not
cost-effective on the grid.  It would be much more efficient to design
the buildings for daylighting and eliminate the need for electricity
in the first place.  Eliminating electric lights also reduces the need
for air conditioning and the electricity it demands, and daylighting
is just plain *nicer*.

# there was a way to capture the heat behind the photovoltaic panels
# at Leslie in the setup where they were not flat against the roof.

In general, this is not a good idea.  Silicon PV panels work best when
they are as cool as possible, and solar heating works best when things
are insulated (unglazed systems like SolarWall notwithstanding).  You
can't design an efficient system to serve conflicting purposes, and
reducing the cost-efficiency of the most expensive components you can
buy is just silly.  Unless there is some shortage of area for grabbing
sunlight, it makes sense to devote different parts for each purpose.

# In Belgrade many of the apartment buildings were centrally heated with
# steam from somewhere, which I suspect may have been generated at the
# same time as electricity.  Is that being done in this country at all?
# Could the U of M generate its own electricity from natural gas and
# use the waste heat?

Not only could the U of M do this, the U of M has been doing this since
before there was a natural gas line to its heating plant on Forest/Huron.
Before that there was a rail spur coming up from the river, which carried
coal to stoke the flames beneath the University's steam boilers.  The
turbines produce much of the juice to run campus, and the spent steam
heats central campus, the dorms and IIRC the hospital as well.

# There is a house in Dexter area which is selling power to the grid when it
# generates too much, and therefore does not need to bother with batteries.

This is an even more fundamental error of thought.  You don't need
to bother with batteries when you have an excess of power, you need
them when you have a deficit.  Selling and buying are different things.
Batteryless, grid-tied PV systems are still a hobby and a social
statement, not yet a way to save money for most uses and users.
That will come someday (there is nothing inherently expensive about
photovoltaic panels), but it isn't here yet.

In general, the "greenest" as well as cheapest way to go is to avoid
the need to use energy to achieve your purposes in the first place.
Designing buildings with top-notch insulation, daylighting, thermal
mass and easy ventilation is going to beat any effort to fix the lack
of those things after the fact with solar-this or wind-that.

The people who actually live on alternate energy learned this long ago.
There is a whole set of appliance makers like SunFrost, whose price
premium for e.g. a refrigerator which uses 1/3 the juice of an Amana
is a lot less than the cost of 3 times as many solar panels and batteries.

Passive-solar design elements make a lot of sense for most buildings.
They don't get used as often as they should because design is usually
done by architects, while total cost of ownership is usually figured
by engineers hired to make the architect's idea work.  If the clients
got more and better information at the beginning, our buildings would
probably be cheaper to run as well as better for us.

response 2 of 157:

Oct 8 02:07 UTC 2002

Nah, use them as motors.  Self-unrolling toilet paper.  It'd be the ultimate
in luxury!

There's still a lot of "low hanging fruit" to be grabbed in energy
efficiency.  For example, most commercial buildings I've worked in have been
large single-story affairs (lots of surface area) with no roof insulation
other than what's provided by the acoustic ceiling tiles.  Heating and air
conditioning have generally been poorly regulated and poorly distributed; at
one bank I worked at, people at one end of the building would be too hot in
the summer, while people at the other end would be so over-A/C'd they were
hiding space heaters under their desks.  No one could fix this, not even the
local heating and cooling company.  It seems like the technology of
climate-controlling a building should have improved beyond that point by
now.

response 4 of 157:

Oct 8 03:51 UTC 2002

        None of this holds true for, say, solar-thermal production, though.
Panels are great if you're recharing small electrical devices.

response 6 of 157:

Oct 8 18:37 UTC 2002

Ob Solar: I am informed that the vast majority of the 1300 W/m2 that hits the
Earth bounces off. I don't remember the exact figure but it was greater than
99%. This means that my house, for example, my roof (about 80 square meters)
could get less than a kilowatt under the best of circumstances, and will
probably get a lot less - maybe as little as 200 watts. This is about 700
BTU/hr or so. It would be hard pressed to keep up with the water heater, which
is a rather small part of the heating load. Forget about any real work, like
transportation. I do half as well or better pedaling.

response 8 of 157:

Oct 8 18:58 UTC 2002

Also, it locally depends upon the surface: a black surface absorbs almost
all of the insolation, although it also radiates (not reflects) some
depending upon its temperature. Solar heaters are made to absorb nearly
all the insolation.

response 10 of 157:

Oct 8 22:43 UTC 2002

I got a chance to look at Slashdot and they mentioned the results of
the Solar Decathlon competition (sponsored by the Department of Energy).
See http://www.eren.doe.gov/solar_decathlon.  Some of the techniques
used by the winners could be useful for many buildings; for instance,
the slat-blinds used on one can be used to either exclude sunlight or
bounce it off the ceiling according to need, cutting the need for
heat, air conditioning and electric lighting.  Another is the vacuum
insulated solar collectors which heat the water on another.

If a new Ann Arbor school building is going to incorporate elements
for efficiency, blinds and water heating make a lot more sense than
photovoltaic panels.  Co-generation from the heating plant is another
good one; perhaps an off-the-shelf microturbine could serve.

The latest issue of Solar Today has a study of a home-improvement
outlet which incorporated a number of conservation and alternate-energy
techniques.  I'll post details when I get time to scare the magazine
up again.

response 12 of 157:

Oct 9 01:56 UTC 2002

As promised....

The September/October 2002 issue of _Solar Today_ has an article on
a retail center in Silverthorne, Colorado.  There is a Sears store,
a floor covering/furniture store, a home improvement store and a
drive-in warehouse in the complex.  They use a variety of different
techniques for reducing energy demand (see the article).  These include:

-       High-performance building envelopes.
-       Radiant-floor heating.
-       Transpired solar collector (unglazed collector for heating
        warehouse ventilation air).
-       Demand-controlled ventilation and natural cooling.
-       Solar electricity.
-       Energy-management system.

Payback times vary widely by technique.  On page 62, some payback times
are given (but no supporting figures); the warehouse skylight system pays
for itself in 2-3 years, the compact-fluorescent lighting system in 4-5
years, and the photovoltaic system in ~30 years.  NREL monitoring shows a
41% energy savings and 58% cost savings; the cost savings are larger due
to the reduced use of expensive electricity and the substitution of natural
gas for space heat to compensate for the reduced thermal output.

Total cost reduction is about $0.61/ft^2/year.  I suspect that this would
have been larger if the more cost-effective techniques (daylighting,
insulation) had been used more heavily and fancy PV had been omitted.
One building also has an electric (!) snow-melting system for the roof.
This would probably have been better replaced by use of pumped groundwater
to melt snow, a la the Rocky Mountain Institute's headquarters.

response 14 of 157:

Oct 9 02:10 UTC 2002

The cost benefits for efficient systems need to be increased, to make them
a better option for all kinds of buildings.  If Walmart suddenly decides to
go efficient, the effect would be huge--I'd like to see it become a strong
interest of theirs.  Too bad that'll never fly in Congress.

response 16 of 157:

Oct 9 02:19 UTC 2002

Amorphous silicon panels are said to work just as well at high as at low
temperatures.  In Michigan the sun does not shine a whole lot in the winter
but shines more than you want it to in the summer, and it shines stronger in
the summer (the Northern Hemisphere is tilted towards the sun in summer, away
in winter).  Detroit Edison sends out graphs of its solar generating results
and the summer months are much better than the winter months. If you were to
adjust the angle to maximize summer collection rather than maximize winter
collection, so as to get the maximum generated power over the whole year, and
could sell it for at least what you paid for it (at a time when there is more
demand), solar power would probably still not pay for itself but would come
a lot closer.  And you would not need batteries as the power company would
buy your summer excess and sell you what you needed in winter when their other
customers did not want as much.

We are building  a house that does not need air conditioning, with lots of
insulation, daylighting, nighttime ventilation, thermal mass, etc.  It will
use most electricity during winter off-peak hours (7 pm to 10 am) for heat
and light.  Businesses may not need light in the evenings but houses do.

Batteries are about 15% of the cost of the Leslie Science Center solar power
system, and they need replacing more often than the other components and take
up space and need maintenance.  You would need an invertor large enough to
handle summer loads in order to convert the DC to AC to put it back on
thegrid.  Other states are paying prices for solar power closer to what they
pay for other on-peak power.  

I can post solar gain through a vertical surface for various months, at our
location (assuming the sun in shining, which is rare in November), also the
Detroit Edison results if I kept them.  We donate $8/month to get a small
fraction of our power from their installation west of town.  They are thinking
about wind power now- wind is stronger when sun is weaker, on average, in MI.

By people not knowing better using air conditioning, I meant that they live
in poorly insulated houses, don't have sense to ventilate at night and close
up in the daytime, run air conditioning with the windows open when it is hot
out, and with the windows shut when it is 60 out and they are cooking, etc.
Jim's sister never takes off her storm windows and keeps the house 68 all year
long.  In summer the basement is about 50 or less (she also air conditions
that).  The Ann Arbor library is the same temperature all year long, or maybe
a bit warmer in winter.  This is not comfortable for people who dress for the
seasons.

response 18 of 157:

Oct 9 11:45 UTC 2002

The disadvantage I can see for the "living roof" is that the
delay of runoff means that the weight of precipitation has to
be carried by the structure until it does run off; this could
mean a substantially stronger (and more expensive) structure
is required.  OTOH, if the roof can be made into another usable
space it could pay off for a school building - being able to
hold lunches, lectures and science/nature classes on the roof
would add to function space during at least part of the year
without needing either additional land or enclosed volume.

response 20 of 157:

Oct 9 14:56 UTC 2002

FWIW, my very poorly insulated house hardly ever needs a/c (I have a 
window unit that I use on only the hottest, most humid days.) My 
secret? Trees. 

response 22 of 157:

Oct 9 15:51 UTC 2002

Yes, I open the windows when I get home from work (around 6p) and leave 
them open all night until I leave for work in the morning (around 8a). 
I have found that with the windows closed, the house stays pretty cool 
until about 1p-2p. I have fans that I run to help bring air in during 
the night and that helps a lot. Another way I avoid having to use A/C 
is by doing things outside of my house on really hot days. It doesnt 
hurt that some of my favorite things to do are swimming, sailing and 
kayaking, all of which are very nice things to do on really hot days. 

But, sometimes I cheat too. Sometimes on *really* hot afternoons, I go 
to the movies because they have air conditioned theaters. 

response 24 of 157:

Oct 9 19:43 UTC 2002

On hot days you can go to a public library and shiver.  For free.
Slynne seems to be doing it all right - fans also help keep you cool in the
daytime when the windows are shut, if you point them at you.  Cooking outdoors
(plug in an electric hotplate) also helps, or cook only after opening up at
night or before closing up in the morning.

We have friends who complain that they are hot and turn the air conditioning
temperature down while wearing long pants and undershirts.  We are wearing
shorts and have to bring warm clothing when visiting them.  Businesses often
require employees to wear warm clothing in summer (nylons, pants) thereby
wasting lots of energy.  My apartment is tolerable up to 83 until the sun hits
the west wall and it radiates.  Insulation would help, as would removing the
brick fireplace.