Power from the Sun

The sun is a reservoir of power almost beyond description.

Man's Dream of tapping this mammoth source of energy has only started to become a

reality and this is the century of science.

WGBH FM in Boston presents the century of science

produced under a grant from the Educational Television and Radio Center in cooperation with the

National Association of educational broadcasters. This is an exploration

of developments in 20th century science and of the implications they present for

contemporary American society. Your host Volta Tory

former editor of Popular Science and now director of radio television programming for the

Massachusetts Institute of Technology.

We have more energy at our fingertips now than ever before. All sorts of

things can be done by pressing buttons. The energy that has made this possible has

come largely from coal and oil. We're using such tremendous quantities of

these fuels that people wonder how long the supply will last. It would not occur to

any sensible person to waste fuel oil by simply letting it flow out of a garden hose

under bare ground. But the sun burst as much energy onto an acre of

land noom as such a stream of oil would contain the sun in fact

freely gives every square mile as much energy per day as there is in a couple of

atomic bombs. If this solar energy could be captured and tamed it

could save us tremendous amounts of work and worry. Professor

height see Hottel of the Massachusetts Institute of Technology is one of our

country's leading authorities on fuels combustion radiant heat transmission and industrial

furnaces. He has been honored by both the American and British governments for his work.

He is the director of the fuels Research Laboratory at MIT and chairman

of the MIT research committee on solar energy. He is here now to

tell us about efforts to harness solar energy.

Professor Hoddle Why is solar energy so much more difficult to handle than

the energy and fossil fuels.

Well Mr. Troy I assume you mean by difficult to handle

difficult to handle economical way or with good economic

consequences. This analogy to the garden hose can be continued

by pointing out that unfortunately the flow isn't all

at one spot from the acres accumulation it's distributed over the

acre and it is that low density of energy or dilute

mists of sunlight. That makes it so hard to devise

a means of cheaply using it. The

mean intensity of sunlight in the United States is about

13 hundred units

falling on a square foot in a day a 24 hour day.

That's to be compared with. Almost.

2000 times that great energy

transfer in the devices that are involved in our

converting fuel power over to fuel energy over to power.

As solar energy. Something that scientists have been trying to capture

or shall we say concentrate for a long time or is this a comparatively new

field of research.

It depends on how old you are the effect they have or the

main stream of effort started back in the

1870s with some French and some

American research.

I think when my properly say that in the present the

more intensive attack on the problem. Started in the

1930s with. The foundation by I got

for a cab. Of a project at MIT and another at Harvard

and by the formation and rush of the helio Technical

Institute.

I have to assume there are various approaches to this problem like the professor I

have. How many are being pursued and how many are of interest.

Well you might broadly divide the field into. About. Three.

Divisions photochemical attack on the problem is one

photo electrical studies institutes another.

And then comely thermal studies with or without

focusing devices to increase the intensity.

Could you define those just a little bit more just what do you mean by the photochemical for

example.

Well I referred to the possibility of in some way

imitating nature's use of sunlight. To grow.

Food. The storage of solar energy in the form of chemical

energy and something that I think by combustion or by being eaten

can furnish energy.

Photo electrical I suppose would be more like a solar battery that we have

yeah absolutely.

The exposure meter of the camera and those just as an example of the.

Photo electrical conversion on a minute scale. The

solar battery is a.

Is the same device developed as far as it's been possible so far

some 11 percent I believe is the efficiency of the best of the present

solar batteries and other thermal On the other hand that would be to use

the heat directly not to transform it into chemical energy or unless this

thermal approach refers to the absorption of the heat

by a blackened surface either a surface of the full

extent of the solar beam being intercepted are a smaller

surface at the focus of some concentrating device

for the purpose either of obtaining energy at a modest

temperature level.

For house heating or refrigeration RS distillation are

possible a far obtaining heat at a higher temperature level and using it to

run what. In. Thermodynamic parlance we call a heat engine.

It's basic to our present power plant which is this approach as

Professor hostile to you think is the most promising.

Or can you say. Well in the long run.

Believe thought a chemical on photo electrical approaches are the

interesting and intriguing ones the ones that would constitute

the neatest solution to the problem. But

there aren't any good ideas at present on how to. Convert.

Soil and sunlight by either of these means at a cost which is

attractive in competition with him. The thermal method on the

other hand is much closer to being economically sound today

and I suspect that within the next few years perhaps the next decade or

more. The one of the thermal approaches will be

one which is economically the soundest.

What kinds of basic research would be most helpful in overcoming

some of these difficulties. You know other words what is there that the

scientists and engineers don't know.

That would be very helpful if they knew more about.

Course when you mention basic research there's always the question how basic

you're asking when we don't know the answer what do we need to

know and what is out. And that's always a tough one but

it's very safe to generalize that.

Since we haven't today any knowledge

which is very impressive from the standpoint of applicability

to an immediate solution of the problem of using sunlight. It

follows that whoever.

Presents a solution will do so as a result of.

Having a fundamentally broad education. Well I've studied.

Physics and chemistry and mathematics if we're talking about young people. He will

have become an expert in one of those fields

rather than set for himself. The goal of becoming a solar

engineer let's say. What tends to be the way. Young people

think they way they back out a narrow field and think they can prepare themselves for it.

When an educator would say that. They should use it simply

as the impetus to study but not an hour of their.

Curriculum to subjects the results of which they

can see applicability out.

Well wouldn't this really cover quite a variety of so-called I think Demick

disciplines. If you are really going to get into the fundamentals of

utilization of solar.

Yes I'm quite sure it does. For example if we are to

find the info to chemical reaction that will produce energy

storage we must know. More than we do today about

the kinetic set of chemical reactions involving both

a chemical acts and the energy storing reaction and the

dissipating reaction the dark reaction so call the one that undoes the

job that the sunlight is trying to do.

That's intriguing what you have in the dark reaction that's new to me.

Well suppose a plant a leaf is growing in the

sunlight. This means that CO2 and

water are being synthesized to form a carbohydrate.

Using energy from the sun.

At the same time look this is going on a degradation is going

on and using up some energy in the case of the

plot belief of the degradation is not very great so there's a

net growth that is quite considerable. When we try to imitate this in a

test tube such as Professor Heights experiments with

the use of Siri I'm Salt's to cause sunlight to

decompose water in the hydrogen oxygen. About thirteen hundred and

ninety nine fourteen hundredths of the energy of that is used.

Usefully is destroyed by a back reaction that does what

we would like to have done. And

the kinetics of the dark reaction must be known in order to

exploit the reaction that we want to have.

Take place. That probably entails a great deal of laboratory work yesterday.

It calls for a general knowledge of photochemistry rather than on knowledge that's

based on any specific desire to use the photochemical

process to make chemicals out of sunlight.

Similarly in the field of physics. There are a number of

places where we now see need far more knowledge of solid state

physics for example. To improve.

Our knowledge of how to build a blocking layer of photos so a battery

are to improve our knowledge of how to make surfaces.

Selectively black. These are

only two examples of where solid state physics. Would

be a significant contributor to that is a

familiar territory.

Ever buy a TV but whatever I bench that other people they always ask me what

is solid state physics.

Could you explain a little why you designate a part of physics as solid

state physics and what it really covers.

Well I'm a chemical engineer rather than a physicist so you should perhaps be asking

someone else to define this and in any detail as an

example in the. Thermoelectric generation

of electrical energy from heat.

The use of the same principle that. Is involved in

measuring the temperature with a thermocouple. Except that here we would like to feed heat

into the hot junction of a thermocouple and take out some useful electrical

energy. We need to know the effect

of the structure of the solid. On the tendency to

produce this voltage at the junction of the two dissimilar metals.

And we find sometimes that.

The maximum voltage is generated when the two metals.

Are quite similar except for a minute quantities of

impurities indicating the. Profound effect of these

impurities only structure of the solid crystal in the case of the blocking layer

photos.

The two parts of the thin wafer.

Silicone used in the Bell Telephone solar battery.

Are very similar except for parts per million of

contaminants which affect the crystal

structure of the solid. It's knowledge of

the nature of that structure to which people refer when they speak of

solid state physics.

Well is this in general an area in which more qualified people are

needed. Are we where we are in solar energy because of lack of money or

because of lack of people.

Well I think it's much more lack of people than lack of money it's it's a lack of

people. With. Ideas. It's lack of able people.

Many things can be done with fairly modest funds. But.

One. Caught my kid way without good people in the field and we have a great

need for.

More good people. Is there a current demand in the

laboratories and research institutions for.

People especially trained for this sort of work.

No I think it's fair to say that that. We

have not made enough headway in the solar field. To

present today very many applications that are economically

sound house heating. Looks as though it may be

a sound way to use the sun.

Domestic air conditioning as a possibility. Hot water

supply for. Houses for domestic use

is a possibility. There is no present.

Evidence to me of that solar power and come dressed to solar

heat will be economical a son very soon and

consequently there is no requirement for.

Engineers trained in this field that many people have heard of course

about the solar houses that have been built by MIT and others. Some

here near Boston and others in other parts of the country. You had to dissipate that many more

of these houses I take it they are all experimental as of now will be built in the

next few years.

MIT will probably follow the present one with a better design

what's our objective continuously to improve these.

We have to work in the Boston area with the.

Knowledge that solar heating is much further from being

economically sound here than in other parts of the country with fixed charge

on the investment in the solar plant is generally greater

than saving the fuel.

We have hope that the improvement in solar

collectors will be such as to reduce their cost to the point

where. So housing is economically sound even in New

England. Even before that day comes though we can buy

experiments in New England reach generalizations concerning

the economic position of solar housing in other parts of the country where

the solar climate is more favorable.

Is it possible to say draw a light on the map.

And that's much closer to the equator of this much further north solar heating. Is

there is not likely to become economically feasible.

Well that's a little bit of an oversimplification that has been done by various

people in the past.

But not by those who have been involved in quantitative

calculations of what can be expected to happen.

It isn't the CO ness of the winter so much as the intensity of

the sunshine which counts how much you get back per square

foot of collector. Is the important number. A sunny

climate in a high altitude in a fairly northern latitude.

Could produce a position of. Greater

economic soundness for solar heating. Than a mild

climate. In a more temperate zone accompanied let's say

by a high humidity which produces absorption in the atmosphere.

So this way you would do best where you have some altitude. Good

dry right there.

That's ideal sea hostile solar engineer and

chairman of the MIT research committee on solar energy as described three theoretical

approaches for the possible utilization of the sun's power. Robert

J Pelletier research associate in civil engineering at MIT will tell Mr. Torrey

of an actual use of the sun's energy in the solar heated house in Lexington Massachusetts.

Then I'm going to ask Mr. Robert Jay Pelletier to describe the newest of the

MATV solar heated houses. Mr. Pelletier is a research associate in

civil engineering at MIT assigned to the project at one of the popular

magazines is called the Solar experts dream house. How big a house

is this Mr. Pelletier.

Well it contains three bedrooms two baths a kitchen dining

room living room. All in about fifteen hundred square feet of living area not too

small by a conventional family standards. And the houses of course two

stories in height.

Does it look very different from the outside.

Yes it does a little especially from the south side except for the south side

however it looks just like a conventional contemporary design.

Few of the collectors.

That's right the collector forms the entire south side of the house. And what is that like.

Well the collector is composed of 60 rectangles of glass

separated by metal frames and the whole bank of collectors is sloped at an

angle of 60 degrees to the horizontal. Is this black or does it look like a

skylight or what. Actually the background of the collector behind the

glass is black but it appears to reflect sky

formations out as clouds birds trees and so forth and is not at all attractive.

Well how does this collector work. Well let's start from the bottom as an

absorbing surface. We have aluminum sheets with copper tubes clamped to them

at intervals of about five inches. The side facing the

sun is painted dull black to absorb the radiant energy and above that we have two

layers of glass separated by an air space.

Is this ordinary glass special for us.

This is a somewhat special glass. We control it or have had the amount of iron put into

the glass controlled to a low level so that it does not absorb very much of the oncoming

radiation.

In effect as light or heat comes through

this glass under the aluminum plate. That's right and then it is collected

in the pipes as a part.

Well the radiant energy is absorbed by the black surface and then heats the

plate. We have water flowing up through these tubes clamped to this plate and the

water picks up this heat or energy in the form of heat and is

carried off down into the basement of the house to a large insulated tank

and there it is kept until needed by the living space.

This tank is much larger than ordinary oil take which should have a poster of a bag as

well.

It's a fifteen hundred gallon tank which sounds large however when you see it in the flesh it doesn't

appear to be much larger or any larger than the old type called

Pan the water from this tank is then used to heat the house.

Yes we have a water to air heat exchanger and we pass warm water

from the tank through the heat exchanger. We then blow air by means of blower

over the heat exchanger and the warm day or is passed through a system conventional system of

ducting into the living space.

So actually they get warm air that has been heated by hot water.

That's it exactly. We choose a water. Heating system for

convenience of collection and also because we can then provide domestic hot water with

great ease. How hot does the water get Mr both here during the heating season the

heat will probably not exceed one hundred fifty degrees during the summer however the

water could get considerably hotter than that.

Would you normally have enough heat in this water for a dishwasher or a hot shower.

We probably will for most of the year but for this

reason and for the reason that it's only economical to design for 100

percent solar heating in a cold climate such as New England when the

amount of sunshine that we receive during the worst part of the heating season is the least that we

receive at any time during the year. We feel that an auxiliary.

Method of heating is a must as an economic must.

How much of the necessary heat for the house would you actually get from

solar energy. But we hope.

And have designed for about 80 percent 75 to 80 percent

depending on the pattern of the weather during the year. Some years we may

get more and other years we may get less.

But you have an exhilarating system there so that you burn oil as well as

our engine to refuel That's right. And if you had a real co-slept for a long

period without sunshine this suffices to keep the house work.

Yes as a matter of fact it has to be of a size sufficient to do the

entire job by itself. Because just as you mentioned we can get the

coldest weather and the worst sunshine simultaneously so that we can't get much

of any help from the solar system in a situation like that is this is just a

Mr Pelletier where you can use this energy to cool the house for air conditioning in

the summer. Not at present we don't seem to have

developed a good practical method of refrigerating with low temperature

water such as we are a low temperature in the in the conventional sense

that we obtain from a collector of this type.

Well how much fuel do you normally need in this house and doing

what.

Well let's first say how much we would require if we didn't have a solar collector. Yes and that would be

about twelve hundred young ones. That's well insulated house and

uses somewhat less fuel than a conventional house of its size would anyway. With the

collector However we should be able to reduce the oil consumption to

about 250 gallons. This means that we're only using about 20

percent of the fuel ordinarily required.

Did you have to use unusual materials or especially skilled labor to build this

Mr poeta.

Not really the collector itself was the only unusual piece of

equipment in the house as such and even the collector was

made of conventional sheet metal and conventional tubing put

together in a slightly unusual fashion but nothing beyond the range of

steels ordinarily employed in building construction.

The rest of the system the heat storage system and the distribution system are all

formed of conventional components that is components readily available in the

present market. They are hitched together in unusual ways and

this caused a little complication.

Is this something that ordinary plumber or heating engineer can handle lower.

Once the plans have been worked yes we think so there are really no

unusual situations occurring in the system that haven't already occurred in other

types of heating systems.

Well Buster but I gathered from Professor Hart of his remarks a little earlier

that solar heating is not regarded as economically

attractive yet. What made the heating system that you have used in this

house unusually expensive.

I think I would attribute most of the expense to the fact that we haven't ever built one of

just this form before. The first time through any design is

always necessarily expensive. We usually have to backtrack from

mistakes or wrong direction somewhere in the building of the thing. I think

in this case we could say that the collector itself was the most expensive although it

perhaps shouldn't be.

And when put into reasonable scale production

what do you see as the future potential of this house Mr.

Botha.

I think one of the chief things to look for in the future is

refrigeration of the solar energy this will enable one to use the

collector to its fullest capacity all year long and will be able to pay for

itself in much shorter order and also gain a lot of

use in areas where there is abundant sunshine but only a moderate need for heat.

At present time they certainly could use a lot of cooling.

It is a great deal of work being done. That method of cooling the

US by means of solar heat.

There is some work being done at present and I'm sure there's going to be a great deal of work done in the future.

You have heard Robert J Pelletier one of the designers of the solar heated

house in Lexington Massachusetts. And research associate in civil engineering at

MIT earlier voted Tory talked with C hostile solar

engineer chairman of the MIT research committee on solar energy and professor of

chemical engineering power from the sun has been a part of a

century of science a recorded exploration of developments in science and their

import for the 20th century American. This series is prepared by

WGBH FM in Boston for the Lowell Institute cooperative broadcasting

Council. Your host Volta Torre a former editor of Popular Science

now director of radio television programming for the Massachusetts Institute of Technology

Director for the series Lillian Ambrosio producer Jack the Summerfield

Bill kavanah speaking century of Sciences produced under a grant from the

Educational Television and Radio Center and distributed by the National Association of

educational broadcasters. Next week Harlow Shapley Payne

professor of practical astronomy emeritus at Harvard University will answer the question

why study stars. This is the end E.B. Radio

Network.