Category: Energy

Thou shalt save energy

I’m not sure anyone else is saying this, so I will: I think **there is
a clear and unambiguous scriptural mandate to reduce our current
energy consumption**.

Now before you dismiss this post, this author and this blog as just
another bible-thumping fanatic, remember that in certain countries,
certain political parties profess strict adherence to Scripture while
being overtly skeptical about the whole climate warming problem. I
think they are wrong and here’s why.

Let’s first review why, from a scriptural point of
view, one could in principle argue that whether we take action or let things run
as they are makes no difference. I’ve heard some of these arguments from very good
(christian) friends, and I hope I’m not going to offend anyone by
refuting them later in this post:

* Revelation 21:1 tells us that all of creation will eventually be
destroyed and replaced by a new one:

Then I saw a new heaven and a new earth; for the first heaven and the first earth passed away, and there is no longer any sea.

* God is sovereign, so no matter what we do, things will run according
to His will.

* It is highly arrogant for Man to believe that they can do anything
about the climate.

The last two arguments are probably the easiest to answer. God is
certainly sovereign, but that doesn’t remove our responsibility for
doing the right things and making the right choices in life. In fact,
God intends us to be co-creators with Him and to participate, so to
speak, in the creative act. This point has been persuasively argued
for by several authors such as C.S. Lewis and J.I. Packer.

The big problem with the first argument is that, even though the
current creation is indeed doomed in the long run, God asked us from
the beginning to take care of it, cf. Genesis 1:28:

God blessed them; and God said to them, “Be fruitful and
multiply, and fill the earth, and subdue it; and rule over the fish of
the sea and over the birds of the sky and over every living thing that
moves on the earth.”

See that? Commandment nr 3 in the whole Bible: subdue the Earth and
rule over it. No mention here of letting things run its course simply
because the creation is about (in the biblical perspective) to be
replaced.

Ah but you might argue that this command was given *before* the Fall,
and that everything went downhill since then. You’re right about the
downhill part, but look at this, Gen 3:23:

therefore the Lord God sent him out from the garden of
Eden, to cultivate the ground from which he was taken.

Man is kicked out of the Garden of Eden, and what is he to do?
Essentially the same thing, e.g. rule over the Earth and cultivate it
and take care of it. The only difference being, of course, that now
it’s going to be painful to do so (Gen 3:19).

The mandate to take care of creation is repeated several times, for
instance right after Noah comes out of the Ark after the Flood, Gen
9:1-2:

And God blessed Noah and his sons and said to them, “Be
fruitful and multiply, and fill the earth. The fear of you and the
terror of you will be on every beast of the earth and on every bird of
the sky; with everything that creeps on the ground, and all the fish
of the sea, into your hand they are given.”

Or of course Psalm 8:5-6:

Yet You have made him a little lower than God,
And You crown him with glory and majesty! You make him to rule over
the works of Your hands; You have put all things under his
feet.

God intends us clearly to rule and manage His creation, no matter what
ultimate fate awaits it.

But the real suprise came to me while re-reading the following
(Deut. 22:6-7):

“If you happen to come upon a bird’s nest along the way,
in any tree or on the ground, with young ones or eggs, and the mother
sitting on the young or on the eggs, you shall not take the mother
with the young; you shall certainly let the mother go, but the young
you may take for yourself, in order that it may be well with you and
that you may prolong your days.

This was one of the many commands given Israel before entering the
promised land. The spirit of this passage, and of others like it, is
unambiguous: God is asking us simply to be **utmostly careful in managing our
natural resources**. We are forbidden to view Earth as just a vast source of
riches to be exploited as quickly and efficiently as possible. We are
explicitly commanded to make sure that Earth can go on being such a
source of riches, indefinitely if needed.

(I’ve even read somewhere that the number of years Israel spent in
babylonian captivity, 70, corresponds to the number of years the land
should have been allowed to rest since Israel took possession of it,
but didn’t. Here again, the importance of allowing natural resources
to replenish themselves is evident.)

The concept of “rest” is a potent one in Scripture. We are to rest
once a week. The land was to rest once every 7 years. We were supposed
to leave alone the corners of our fields that weren’t harvested. In
other words, **Scripture is full of passages mandating a careful
management of our natural resources**. Arguing that we can do whatever
we want with Earth simply because it is doomed to the eternal fire
anyway is not only lazy and criminal, it is also doctrinally false.

Posted on by David Lindelöf 2

Equivalent conductance due to air infiltrations

Here is how you compute the thermal coupling between a room’s indoor temperature and the outdoor temperature due to infiltrations.

The equation governing the exchange of heat is as follows:

Cair × dT/dt = g × Δ T

where Cair is the indoor air thermal mass [J/K], T is the indoor air temperature [K], g is the equivalent conductance [W/K] and Δ T is the temperature difference between indoors and outdoors.

What we need to compute is how much heat is exchanged per unit of time when air seeps into the indoor room. The air that infiltrates will draw (or more rarely, yield) heat from the indoor air until it reaches thermal equilibrium with T. So we obtain:

V’ × ρ × Cp air × Δ T = J

where V’ is the infiltration rate [m3 / s], ρ is the air density (about 1.2 kg/m3), Cp air is the air thermal capacity (about 1008 J/kgK) and J is the rate of heat exchange in W.

Now we immediately recognize that actually, J / Δ T = g. But we can also simplify further by noting that air infiltration rates are more commonly given in room volumes renewed by some unit of time (commonly the hour). Note first that:

Cair = Vair × ρ × Cp air

and therefore:

V’ × Cair / Vair = g

or more simply, if Nren is the room volume renewal rate per hour:

Nren / 3600 × Cair = g

And therefore the main equation becomes simply:

dT/dt = Nren / 3600 × Δ T

I find this to be an amazingly simple equation, especially as it applies to other situations similar to air infiltrations. For example, you can use it to compute the exchange of heat among the elements of a heater through which hot water circulates.

Posted on by David Lindelöf

7 numbers why building automation can save the world

Automating buildings costs money. Lots, lots of money. The return on investment (ROI) is usually very low, and it takes a long, long time (on the order of 5 to 10 years) for such an investment to pay for itself.

To make matters worse, people who rent the home or apartment they live in have little incentive to make it energy-efficient. They have no guarantee they will still live in the same place 10 years in the future. And landlords? Why would they invest? Energy costs are always born by the tenants, so they too have little incentive.

If financial considerations won’t motivate people to invest in smarter buildings, here I propose another incentive. Building automation, if implemented globally, is one of the most cost-effective strategies for keeping the atmospheric CO2 concentration at safe levels until 2050.

I reviewed Thomas L. Friedman‘s Hot, Flat and Crowded in an earlier post. In that book, Mr Friedman refers to a paper published by Pacala and Socolow in Science in August 2004.

I’ve traced that paper. You can find it here: Stabilization Wedges: Solving the Climate Problem for the Next 50 Years with Current Technologies. Even if you don’t read the full paper, please do read the first couple of pages. The authors do a fantastic job at summarizing our current situation with respect with CO2 emissions and where we are headed if we do not act now. The abstract speaks for itself:

Humanity already possesses the fundamental scientific, technical, and industrial know-how to solve the carbon and climate problem for the next half-century. A portfolio of technologies now exists to meet the world’s energy needs over the next 50 years and limit atmospheric CO2 to a trajectory that avoids a doubling of the preindustrial concentration. Every element in this portfolio has passed beyond the laboratory bench and demonstration project; many are already implemented somewhere at full industrial scale. Although no element is a credible candidate for doing the entire job (or even half the job) by itself, the portfolio as a whole is large enough that not every element has to be used.

Let me summarize the key figures, and please commit them to memory:

280 ppm CO2 atmospheric concentration

For the most part of human history, the CO2 concentration in the atmosphere remained relatively stable at 280 ppm (parts per million). The industrial revolution coincided with the start of a clear increase in CO2 concentration.

375 ppm CO2 atmospheric concentration

The CO2 concentration at the time of the article (2004). But remember that CO2 concentration has always increased since careful measurements started in the late fifities:

CO2 atmospheric concentration for the past 50 years
CO2 atmospheric concentration measured on Mauna Loa (Hawaii) for the past 50 years, adapted from my thesis.

500 ppm CO2 atmospheric concentration

Even allowing for (healthy) skepticism, most scientists believe that mankind must at all costs prevent the CO2 levels from reaching double the preindustrial concentration, or about 560 ppm. To err on the side of caution, we as a species should pledge never to let CO2 level cross the 500 ppm limit.

7 billion tons of CO2 per year

When Pacala and Socolow wrote the article, mankind was dumping in the atmosphere the equivalent of 7 billion tons of CO2 per year (7 GtC/year). That’s enough CO2 to fill 1 billion hot-air balloons each year. It is also the upper limit of allowed global emissions if we are to stabilize CO2 atmospheric concentrations at their current levels for the next 50 years.

14 billion tons of CO2 per year

If we fail to act now, by 2054 we will be pumping out 14 billion tons of CO2 per year in the atmosphere, according to the so-called Business As Usual (BAU) scenarios. Such an emission rate will almost certainly result in a CO2 concentration of more than 500 ppm, i.e. beyond the safe upper limit. The consequences on global warming can only be disastrous.

Average global temperatures for the last 150 years
Average global temperatures for the last 150 years, adapted from my thesis.

50 years

Stabilizing CO2 emissions is only the first half of the battle. Our goal is to stabilize them at their current levels for the next 50 years, but after that we must devise solutions to reduce them.

7 wedges

The paper proposed 15 potential solutions (or “wedges”) for stabilizing our CO2 emissions. Each one of these is technologically feasible and has been commercially demonstrated. Any of them will prevent the increase in CO2 emissions by 1 GtC/year by 2054. Thus, to keep our CO2 emissions to current levels by 2054, we must implement at least 7 of these 15 strategies on a global scale.

Wedge 3

The third wedge proposed by the authors appears to me as the easiest to implement:

Cut carbon emissions by one-fourth in buildings and appliances projected for 2054.

Yes, that’s right. If we or our children are to make it safely through the second half of this century, we must implement at least 7 of 15 strategies, one of which is the reduction in carbon emissions by 25% in buildings and appliances.

And how, you may ask, can we achieve this? Well, there are really only two solutions. We may switch to more carbon-neutral energy sources, or we may reduce our energy demand. As I’ve argued in a previous post, we should prefer the latter option for the following reasons:

  • Our fundamental problem is our dependency on cheap sources of energy. Carbon-neutral energy sources, although much cheaper than only ten years ago, are still far from competitive.
  • We have enjoyed cheap sources of energy for so long that we have never had to consider the need to reduce our demand. In other words, we are addicted to energy, not oil.
    5 hours energy
    Credits: RogeSun Media
  • It is much, much more cost-effective to reduce the energy demand of buildings and appliances, particularly through better home and building automation, than attempting to replace our current sources of energy with carbon-neutral ones.

Conclusion: an elevator pitch for building automation

We currently emit 7 GtC/year in the atmosphere. If we fail to act now, we will be emitting 14 GtC/year in 2054 and the CO2 concentration will be more than twice its preindustrial level. Building automation, if implemented on a global scale, can make buildings at least 25% more energy effective, which will prevent the emission of 1 GtC/year by 2054, out of 7 GtC/year required to keep at current levels. It is arguably the most cost-effective strategy for mitigating climate change.

Posted on by David Lindelöf

Computing sustainability and building automation

The energy demand of computers—including PCs, peripherals, and corporate data centers—produced about 830 million tons of CO2 in 2007, according to a report by the the Global eSustainability Initiative (GeSI), a group of technology firms interested in the potential impact of information and communication technologies on climate change. But they can also help us save energy—the question has always been how, and how much.

The June 21st issue of The Economist comments on this report, summarizing the areas in which computers can help us achieve CO2 savings. The savings estimated in gigatonnes for 2020 are as follows:

  1. Smart grid: 2.03
  2. Smart buildings: 1.68
  3. Smart logistics: 1.52
  4. Smart motors and industrial processes: 0.97
  5. Transport optimisation: 0.60
  6. Teleworking: 0.22
  7. Videoconferencing: 0.14

Notice that smart buildings occupy the number two spot. Enabling buildings that switch off heating and ventilation when nobody is around will, according to the report, reduce our emissions by more than 1.6 billion tons of CO2. Smart buildings had always been touted as an effective CO2 emission reducer, but this is as far as I know the first time a concrete figure is given for those savings. The total emissions from ICT by 2020 is estimated at 1.4 gigatonnes, or one-fifth of the total savings (7.8 gigatonnes).

One should, of course, be extremely suspicious of such data. I have not read the report itself and can’t comment on the methods used to derive these figures. But even if the absolute numbers are wrong, it is encouraging to see that smart buildings are estimated to contribute 20% of all CO2 savings from ICTs by 2020.

Posted on by David Lindelöf

Monitoring home electricity usage

If you can measure it you can control it, and that is also true of your energy consumption.

Two energy-monitoring devices have recently been brought to my attention that are not only easy to use, but also to install. The first one is the OWL, and consists of a wireless clip you put around your house’s main electricity cable. Data is then transmitted to a portable LCD device. I suppose it works by measuring the magnetic fields induced by the current.

The other one is the Wattson. It works along similar principles, but is maybe just a bit more stylish.

I welcome the introduction of such devices on the market. I’ve heard that when consumption meters were introduced in cars, their owners started paying attention to it and adjusted their driving accordingly. Some do it for genuine economic reasons, but others do it simply for the fun of it. These sort of toys are simply irresistible to us grown-up children.

Perhaps the only, small gripe I could have against the OWL or the Wattson is their lack of granularity. You measure the total energy consumption of the house, and cannot measure the consumption by appliance (fridge, oven, etc) or by kind (lighting, heating, etc). And I don’t suppose there’s any way to record historical data from them. But never mind, they’re cool nevertheless.

Posted on by David Lindelöf

CO2 concentrations and global temperature correlation

CS Lewis called this person the “embarassing enthusiast”. A person very committed and very verbal about your common religion, yet someone who occasionally discredits your own views by advancing weak arguments to support it. What to do with such a person’s views? You cannot oppose them—for that would work against your own. Yet you cannot endorse them either, for you want your creed to be built on unshakable foundations.

I started feeling that way about Al Gore when I read his book, An Inconvenient Truth. Mr Gore’s commitment to curbing world carbon emissions is commendable. We have arguably never seen someone deliver such a passioned message with such energy and impact. And I happen to agree, on the basis of the physical evidence we have, that efforts must be taken to diminish man-made CO2 emissions. So I had hoped that Mr Gore’s book would deliver a message that would be both emotionally and factually flawless—but as it turns out, some of his facts should have been checked.

Last 10 April I was a guest in a meeting of Toastmasters International (EPFL). One of the speakers delivered a wake-up call to all of us who would blindly believe anything coming out from the climate-change lobby. In particular, he pointed out that the famous correlation between CO2 concentrations and global temperatures observed for the past 100,000 years in ice core data, and used as one of the strongest arguments by Mr Gore, is not what we think. There is a correlation, yes—provided the CO2 data is shifted 800 years behind the temperature data.

The original paper from which this data came happens to be on my thesis’s bibliography, so I checked this claim. And sure enough, the authors of this paper show quite clearly that the the CO2 data lags behind the temperature data by 600±400 years—suggesting that historically, CO2 concentration increases have been caused by temperature increases, and not the other way around.

I am surprised that climate-change skeptics have not pointed this out before. But it does not really matter, for the current global warming does happen within the same time frame as a dramatic increase in CO2 concentrations. I do not need to look several ice ages in the past to know that. I only wish Mr Gore had done so too before using this argument.

Posted on by David Lindelöf 2

Energy-efficient appliances in Switzerland

Top Ten is a well-designed and user-friendly website that carries information on energy-efficient appliances and other equipment. It is mainly targeted at the swiss audience but I am sure most of these products can be found all over the european market.

On this site one can also find information on alternative energy sources and pointers to specialized companies that can help with their installation.

Posted on by David Lindelöf