Alternative Energy in our World

| September 14, 2021 | Leave a Comment

Media Type: Article - Recent

Author(s): Gioietta Kuo

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In our enthusiasm to quit using fossil fuels because of their Green House Gas (GHG) emissions, the world is plunging headlong into alternative energy sources: solar, wind, hydro and nuclear.

Yet each of these has its own problems. The most obvious ones are what happens if the sun does not shine, wind does not blow, rain does not fall, or we run out of nuclear fuel? Above all, we tend to avoid asking “How much will it cost?” Or, if we have no choice, then “Can we afford it?”

This article offers an overview comparing all of the alternative energy sources we are developing for our present and conceivable future needs.


INTRODUCTION

In 2020, total US electricity consumption was about

3.8 trillion kilowatt hours (kWh). [1] Electricity is

used in all sectors of economy. It is used for

lighting, heating, cooling and refrigeration and for

operating appliances, computers, electronics,

machinery and public transportation systems.

 

It is estimated that the U.S. electric power sector added 14.8 gigawatts (GW) of new wind capacity in 2020. We expect 16.0

GW of new wind capacity will come online in 2021 and 5.3

GW in 2022. Utility-scale solar capacity rose by an estimated

10.5 GW in 2020. Our forecast for added utility-scale solar

capacity is 15.5 GW 2021 and 16.6 GW for 2022 [2].

 

Figure 1. US Electricity generation by fuel [2]

 

 

The US uses a mix of energy sources and produces many

different types of energy. These can be grouped into

general categories such as primary and secondary,

renewable and nonrenewable, and fossil fuels.

 

Primary energy sources include fossil fuels (petroleum,

natural gas, and coal), nuclear energy, and renewable

sources of energy. Electricity is a secondary energy source

that is generated (produced) from primary energy sources.

 

Energy sources are measured in different physical units:

liquid fuels in barrels or gallons, natural gas in cubic feet,

coal in short tons, and electricity in kilowatts and kilowatt

hours. In the US, British thermal units (Btu), are commonly

used to compare different types of energy to each other. In

2020, total U.S. primary energy consumption was about

92,943,042, 000, 000, 000 Btu, or 93 quadrillion Btu.

 

  1. B. S. primary energy consumption by energy

source, 2020

In 2020, electricity produced by utility scale

generators in the US represented about 60% of all

the electricity generated or about 4,009 billion kWh.

In sum roughly 60% of this amount was produced

from fossil fuels (coal, natural gas and petroleum)

about 20% from nuclear energy and the remaining

20% from renewable energy sources.[2]

  1. U.S. Energy Use by Sector

There are 5 energy use sectors. In 2020 these were [1]:

electric power quads 35.74 %. Transportation quads

24.23%; industrial quads 22.1 %; residential quads

6.54%; commercial quads. 4.32%;

Total = 92.94 quadrillion Btu.

For renewable sources the total was 11.59

quadrillion Btu

Sales of electricity by percentage of the total generated to

major consumer sectors in 2020 [3] were as follows:

Residential 38.9%, or 1.46 trillion kWh; commercial

34.8%, or 1.28 trillion kWh; industrial 25.1% or 0.92

trillion kWh; and transportation 0.2%, or 0.01 trillion

kWh.

  1. SOLAR ENERGY
  2. A. It is possible to have large scale utility solar panels

for industrial uses or for feeding into the grid.

Also roof top residential solar panels on individual houses

are becoming popular to save high electricity costs.

 

 

 

 

 

 

 

Figure 2 A typical utility solar panel installation

of 1-5 megawatts (MW). Spanning acres of land in

desert like locations.

The average house in the United States is between 2,000

and 2,499 square ft in size and uses 11,606 kWh of

electricity annually, or 967 kWh per month [4].

Of course electricity usage depends on the location of the

house. In the USA the Southwest gets the most sunlight,

and a house there that has a south facing roof without any

shading during the day, would require only between 16

and 25 premium solar panels to generate the roughly 1,000

kWh electricity per month. In this case, “premium” refers

to solar panels with an output rating of about 400 watts,

which are the highest efficiency panels currently available.

These include the SunPower A Series and LG NeON 2

series.

 

Budget solar panels can save one money, but will

generate less electricity per panel. The lowest efficiency

panels one can find on the market have a rating around

250 watts. That would mean an average house in the

Southwest would need 24-38 budget solar panels to

supply all of its electricity needs.

 

So what is the cost for society to go solar?

The best solar manufacturing cost analysis may be that of

the NREL – National Renewable Energy Laboratory [5],

which analyzes the manufacturing costs associated with

photovoltaic (PV) technologies, including crystalline silicon,

cadmium telluride, copper indium gallium diselenide,

perovkite, and III-V solar cells. All of these substances may

be evaporated on glass or some other material to make the

panel. Silicon is, by far, the most common semiconductor

material used in solar cells, and represents approximately

95% of the modules sold today.

 

The foregoing analyses are generally based on a bottom up

model with costs for the multiple components used along the

supply chain. In this way, we get a detailed look at the main

cost drivers.

  1. Estimated Cost of Solar Panels

Since 2010. NREL has been adding new information on new

technologies to provide PV cost reductions over time. This

includes new innovations, increased production volume and

other factors could drive future cost reductions.

Based on 2018 prices, here is a breakdown of the cost of

different components which contribute to the sales price of

solar panels in terms of US $.

We derive a Minimum Standard Price or (MSP).*

  • Minimum Sustainable Price (MSP) is what

would need to be charged for a PV technology at any

given time to cover the production and overhead costs

and also to pay back investors.

*. Step by step and total manufacturing costs for a

given process to identify major cost drivers.

* Finally a roadmap is produced to identify

potential pathways for cost reduction in the near future.

 

We start at the bottom of the module, which is silicon. The standard monocrystalline silicon wafer size is around 244

cm2. For 2018 we provide here a breakdown of the different Components which contribute to the cost in terms of US $ per wafer.

In parentheses are given the cost of the item per wafer:

1) Silicon ($0.06);

2) Wafer processing ($0.1);

3) Remaining costs for module assembly ($ 0.02);

4) Remaining costs for cell fabrication ( $ 0.12);

5) Balance – of – module materials ($ 0.17);

6) Cell metallization pastes ($0.03);

7) Research & development plus sales, general administration ($0.07).

Total cost is $0.57 per wafer

Calculated sustainable price is $ 0.67.

 

As time goes on, we can expect reprocessing

advancements, efficiency gains, and economies of scale. So by

2025 the following numbers can be expected:

1) Silicon ($0.01);

2) Wafer processing ($0.04);

3) Remaining costs for cell fabrication ($0.02);

4) Balance – of – module materials ($0.06)

5) Research & development plus sales, general administration

($ 0.02).

Total cost projected for 2025 is $0.15.

Calculated sustainable price is $0.18.

 

Apart from the manufacturing cost we need to factor in

transportation of the delicate PV panels as well as the

installation cost of solar farms [6]. First there is the cost of

land: With all the equipment and space between panel rows, a

one MW solar farm typically needs 6–8 acres, Typical freight

charges for solar panels range from about $150 to $400 for

1- 24 solar panels.

Finally the solar farm installation costs are typically between

$0.82 to $1.36 per watt. That means that a one megawatt (MW)

solar farm would cost between $820,000 and $1,360,000.

Installation by experts may take 2-3 days and cost $800 – $1200.

 

It is interesting to note that so many new PV panels have

come on the market with high power ratings. Trina Solar

recently revealed a panel which will deliver an impressive

600W. Then in August, at the SNEC PV Power Expo in China,

JinkoSolar unveiled a 610W version of their current TigerPro

panel while Trina solar proposed a 660W+ panel is on the

horizon. Interestingly, there were close to 20 manufacturers at

SNEC 2020 showcasing panels rated over 600W.

  1. SOLAR BATTERIES

Of course, the sun does not shine all day long and so storage

batteries are also required. While the solar panel is lapping up

electricity, batteries are necessary for the time when the solar

panels are not accumulating power. Here is a collection of

specifications to consider:

 

* Capacity and Power Rating [7]

These are measured in kilowatt-hours (kWh).. While capacity

tells you how big your battery is, it doesn’t tell you how much

electricity a battery can provide at a given moment. For the

full picture, one also needs to consider the battery’s power

rating—that is, is the amount of electricity that a battery can

deliver at one time, measured in kilowatts (kW).

 

Depending on one’s needs, a battery with high capacity and

low power rating would deliver electricity for a long time,

while one with a high power rating would deliver more electricity but for a shorter time.

 

* Depth of Discharge – DoD [7]

This refers to the amount of a battery’s capacity that has been

used. Most manufacturers will specify a maximum DoD for optimal

performance. For a 10 kWh battery, one should not use more

than 9 kWh before recharging it, very much like a cell phone

or an electric car.

 

* Round trip efficiency [8]

Round-trip efficiency is the percentage of electricity put into

storage that is later retrieved. The higher the round- trip

efficiency, the less energy is lost in the storage process.

According to data from the U.S. Energy Information

Administration (EIA), in 2019, the U.S. utility- scale battery

fleet operated with an average monthly round-trip efficiency

of 82%, and pumped-storage facilities operated with an

average monthly round-trip efficiency of 79%.

 

This represents the amount of energy that can be used

as a percentage of the amount of energy that it took to

store it. For example, if you feed 5 kWh of electricity into

your battery and can only get 4 kWh of useful electricity

back, the battery has 80 percent round-trip efficiency

(4 kWh / 5 kWh = 80%). Generally speaking, a higher

round-trip efficiency means you will get more economic

value out of the battery.

 

* How long do solar batteries last? [7]

Most solar batteries on the market today will last

somewhere between 5 to 15 years. While that i s a significant amount of time, you will likely need to

replace them within the 25 to 30+ year lifespan of your solar system.

 

One might ask why this is such a varied range. There are

a couple of factors, including the type of battery you install,

how often you use the battery, and where the battery is

stored that will have a significant impact on how long the

battery lasts.

 

  1. TYPE OF BATTERY [9]

Batteries used in home energy storage typically are made with

one of three chemical compositions: lead acid, lithium ion,

and salt water. The total cost of solar battery installation tends

to fall in the $11,000 to $18,000+ range or $800 to $1,300 per

kWh. In most cases, lithium ion batteries are the best

option for a solar panel system, though other battery types can

be more affordable.

 

Bigger factories, the use of automation and more efficient

production methods, produce better with less materials waste

for the solar sector. The average cost for a solar panel

dropped by 90%. From 2010 to 2020. [10 ]

 

=. Lithium ion Batteries

This is the best for a solar combination. Currently 89% of

new energy storage capacity installed uses lithium ion

batteries [11]. Lithium ion batteries are lighter and more

compact than lead acid batteries. And they are rechargeable.

 

They also have a longer lifespan. In 2020 the price is $137/

kWh [5]. and is predicted to drop to around $100/kWh by

  1. However, lithium ion batteries are still more expensive

than their lead acid counterparts.

 

= Lead acid Batteries

This is a long tested technology that has been used in off grid

energy systems for decades. While they have a relatively short

life and lower DoD than other battery types, they are one of the

least expensive options currently on the market in the home

energy storage sector. For homeowners who want to go off the

grid and need to install lots of energy storage, lead acid can be

a good option.

 

= Saltwater Batteries

This new technology is easily dispensable, but not yet fully

tested. It offers medium cost and medium lifespan, but

maximum DoD. Unlike other home energy storage options,

saltwater batteries contain no heavy metals, relying instead

on saltwater electrolytes. While batteries that use heavy

metals, including lead acid and lithium ion batteries need to

be disposed of with special processes, a saltwater battery can

be easily recycled.

 

  1. A NOVEL TECHNOLOGY. COMBINING SOLAR CELL

AND DESALINATION [13]

As global overpopulation is rapidly increasing and we are

relentlessly using up our resources, fresh water scarcity has

become a severe global problem. According to a recent UN

report, already over 2. billion people live in countries

experiencing high water stress. Therefore researchers in Saudi

Arabia and China are developing a novel technology using a

combination of solar power generating electricity while at the

same time using its waste heat for desalination of seawater. It

is claimed that both these processes are highly efficient,

producing little waste brine and cutting its potential

environmental impact.

 

The process involves a highly complex multistage device

called a PV membrane distillation-evaporative crystallizer

(PME). PMEs consist of a solar panel on top of a multistage

membrane distillation (MSMD) component. The MSMD uses

waste heat from the solar cell to drive water evaporation, and is

designed to collect and reuse latent heat from vapor

condensation at each distillation stage to drive evaporation in

the next stage.

Clearly solar power is an attractive option for producing clean energy. But its limitations (expensive set-up, limited operational hours, the need for storage batteries and long transmission lines) mean that other sustainable energy sources are also needed.

  1. WIND ENERGY [10]

Wind turbines use blades to collect the wind’s kinetic energy as

it flows over the blades to run a generator. Wind blades are

mounted at about 100 meters above ground to catch the

stronger less turbulent wind. The turning shaft spins a

generator to make electricity. A stand-alone wind turbine is

typically used for water pumping or communications. Farms

and ranches may use it in windy areas.

 

Over the last 30 years, many advances in the use of wind

energy have grown over the world. As with solar energy, much

space is needed and many turbines are connected by heavy

duty cables leading the electricity to a distant grid.. High costs

are incurred not only for construction and maintenance of the

turbine itself but also for the cables which may cost 1 million $

per mile. Most commercial scale turbines installed today are

about 2 MW in size. U.S. total annual electricity generation

from wind has increased from about 6 billion kWh in 2000 to

about 300 billion kWh in 2019, accounting for about 7.3% of

total utility electricity generation.

 

 

 

 

 

 

 

 

Figure 3. A large wind farm at sunset

So what does it cost society to go into wind energy?

  • Cost of Home or Farm Scale Wind Turbines [14]

Wind turbines under 200 kilowatts cost roughly

$3,000 – $8,000 per kilowatt of capacity. A 10

kilowatt machine which is the size needed to power

a large home would have an installed cost of

$50,000 -$80,000. But it is more practical to

consider setting up a wind farm because there are

great economies of scale. On average a commercial

wind turbine may cost $2.6 – $4 million. Typically

the cost is $1.3 million/MW of electricity producing

capacity. Most turbines of this category have a

capacity of 2-3 MW so most turbines cost in the

$2-4 million range but the electricity generated can

be as high as 12 MW. Cost increases with size but

complexity and construction of the overall farm site

may benefit from having larger turbines. Each blade

has to be manufactured with high quality and

reliability.

  • Installing a wind farm [15]

There are many constraints. These include highway underpass

heights that may limit the size of wind towers, the availability

of cranes able to lift and install nacelles, and the trucking

fleet’s difficulty in transporting longer wind blades. A study

released by the Energy Department, Enabling Wind Power

Nationwide, concluded that the technological innovations

enabling the development of very large wind turbines have

significant potential to reduce the cost of wind energy.

However, transportation and logistics challenges are limiting

the size and height of towers and turbines still remain.

  • Underground vs overhead power line installation [16]

Because of unpredictable weather conditions, there are many

benefits to underground cable transmission, even though their

initial cost may be 4 to 14 items higher. These advantages

include shorter repair times for the same voltage and distance,

less danger of starting fires, etc..

A typical new 69 kV overhead single-circuit transmission line

costs approximately $285,000 per mile as opposed to $1.5

million per mile for a n ew 69 kV underground line (without

the terminals). A new 138 kV overhead line costs

approximately $390,000 per mile as opposed to $2 million

per mile for underground (without the terminals).

* Operation and maintenance costs [1]

Operation and maintenance costs may add $42,000 – $48,000

per year according to research on wind turbine operations.

Operation and maintenance costs constitute a sizeable

share of the total annual costs of a wind turbine.

For a new turbine, costs may easily make up 20-25 per cent

of the total cost per kWh produced over the lifetime

of the turbine. These costs may include: rent of land;

insurance; routine maintenance; repair; spare parts

and administration.

  • Trucking and associated gas costs [18]

Depending on the distance between the finished product

leaving the factory to the location of the wind farm, it is

0difficult to estimate the final cost, but transportation and

construction are both sizeable components.

The nacelle that sits atop the tower or pedestal can weigh 75

tons, and the three-blade assembly can weigh 36 tons, or

about 12 tons per blade. The pedestal, or tower that supports

the nacelle, weighs on the order of 24 tons.

Current estimates indicate that it costs $100,000 to $150,000

to transport blades from either a port of entry or manufacturer

to a wind farm. As component parts of wind generators increase

in size, these costs can be expected to increase dramatically.

Wind-power too has much to recommend it as a source of sustainable energy. But again there are drawbacks such as high construction costs, difficulties transporting components to the wind-farm site, and unpredictable interruptions in service that demand significant energy storage capacity. So we would do well to consider further options.

III HYDRO ELECTRICITY ENERGY [19]

Energy from moving water is the most commonly used

renewable source of electricity. Hydro-energy, is a form

of renewable energy that uses the water stored in dams, as

well as flowing in rivers, to create electricity in

hydropower plants. The falling water rotates the blades of

a turbine, which then spins a generator that converts the

mechanical energy of the spinning turbine into electrical

energy.

 

 

 

 

 

Figure 4. A typical hydroelectric dam

 

 

 

 

 

 

Figure 5. The world’s second largest hydropower station –

Baihetan on the upper Yangtze River between the. provinces Yunnan and Sichuan in the People’s Republic of China has just started operation

China is the largest producer of hydroelectricity.

The Three Mile Gorge Dam which holds back the

Yangtze River is the largest hydroelectric dam in the world

and has enough generators to produce 22,500 megawatts

of power. Other top producers are located in the US, Brazil,

Canada, India and Russia.

 

Around 60 % of all renewable electricity is generated by

hydropower [19][20] which produces about 17 % of total

electricity production from all sources including nuclear and

fossil fuels, and 70 % of all renewable electricity . This is

expected to increase by 3.1% each year for the next 25 years

[20] [21]

Advantages to Hydroelectric Power [22][23]

  • No fuel is burned so there is minimal pollution
  • Water to run the power plant is provided free by nature
  • Hydropower plays a major role in reducing greenhouse gas emissions
  • Relatively low operations and maintenance costs
  • The technology is reliable and proven over time
  • It is infinitely renewable since rainfall replaces the water in the reservoir except in the event of drought when output may be much reduced.

Disadvantages [22][23]

  • High investment costs for construction.
  • Output depends on hydrology (rain and snowfall) habitats
  • In some cases, loss or modification of fish habitats
  • May halt or complicate fish migration patterns
  • In some cases, changes water quality in rivers and reservoirs
  • May require the displacement of local populations

Hydropower and the Environment [23]

Hydropower does not pollute the water or the air. However,

hydropower facilities can have significant environmental

impacts by affecting land use, homes, and natural habitats in

the area near and below the dam.

 

Most hydroelectric power plants have a dam and a reservoir.

These structures may obstruct fish migration and affect their

populations. Operating a hydroelectric power plant may also

change the water temperature and the river’s flow. These

changes may harm native plants and animals in the river and

on land. Reservoirs may cover people’s homes, important

natural areas, agricultural land, and archaeological sites. So, building dams can require relocating people. Methane, a strong

greenhouse gas, may also form in some reservoirs and be released into the atmosphere.

 

Taken together, Solar-, Wind-, and Hydro-power all provide

valuable means of generating electricity. Yet current and

foreseeable future demands for electric power are so great that still other options deserve careful consideration.

  1. NUCLEAR FISSION

Nuclear power is the only energy source that delivers reliable energy 24 hours a day.

At present nuclear energy provides 55% of carbon free electricity in the US [24].

 

A typical nuclear reactor uses Uranium-235. Natural uranium

contains only about 0.7% Uranium- 235, with the remainder

being an isotopic mixture consisting mostly of Uranium- 238

[25]. The fuel might cost $5,500/kW – $8,100/kW or between

$6 billion and 8 billion for a 1,100 MW plant. [26]. Even

though this cost is high, once built, operating costs are much

lower consisting solely of the fuel cost and the disposal of

fission products. This last however poses location and

political problems.

 

A fission reactor contains and controls a nuclear chain reaction

which produces heat through nuclear fission. This heat is used

to make steam that spins a turbine to create electricity. There

are 440 commercial reactors worldwide, including 94 in the

US.

  1. Types of light water reactors in US [27]

==. Pressurized water Reactor -PWR

More than 65% of commercial reactors are of this type,

which pumps water into the reactor under high pressure to

prevent the water from boiling. The water in the core is

heated by fission and then piped into tubes inside a heat

exchanger.

These tubes heat a separate water source to create steam

which then turns an electric generator to produce electricity.

 

== Boiling Water Reactor – BWR

It heats water and produce steam directly inside the reactor

vessel. Water is pumped up through the reactor core and

heated by fission. Pipes then feed the steam directly to a

turbine to produce electricity. The unused steam is then

condensed back to water and reused in the heating process.

 

In 2019 31 countries had commercial nuclear power plants of

which 14 supplied at least 20% of the nation’s total electric

output. The US has the greatest nuclear electricity generation

capacity.

  1. Top 5 nuclear electricity generating countries in 2019

[28] :

For US nuclear electricity generation capacity is currently 98

MkW; Actual electricity generation is 809 BkWh;

With 19% of total electricity used nation wide. For France, nuclear electricity generation capacity stands at 63 MkW; with actual electricity usage at 382 BkWh; of which nuclear accounts for 70%

 

For China , the figures are nuclear electricity generation

capacity is 46 MkW; actual electricity usage is 330 BkWh;

and nuclear’s share in the country is 5%

For Russia, nuclear electricity generation capacity stands at

28 MkW; and total electricity usage at 196 BkWh, of which

nuclear accounts for 14%.

For South Korea. Nuclear electricity generation capacity

is 23 MkW; total usage is 139 BkWh; and nuclear’s share

is roughly 25%

  1. BREEDER REACTORS [29]

A breeder reactor produces more fuel than it uses, and is

often touted as the answer to uranium-scarcity, which may

affect conventional reactors. However breeders are also

dangerous as they produce weapons–grade Plutonium and

thus pose a terrorist risk.

 

Nuclear reactors utilize the heat generated during fission of

atoms to produce energy. Breeder reactors contain an inner

core of the Plutonium isotope Plutonium-239 . This core is

surrounded by a shield of the uranium isotope Uranium 238.

When bombarded with neutrons, Plutonium splits to produce

smaller fragments, releasing heat energy, and more neutrons.

Some neutrons hit the surrounding Uranium-238 atoms which

is transmuted into Plutonium-239, effectively producing the

fuel itself. The remaining neutrons bombard other Plutonium

atoms, starting a chain reaction which produces more energy

and neutrons. When all the surrounding Uranium is converted

to Plutonium, the fuel is completely regenerated. A breeder

reactor is named so because it ‘breeds’ its own fuel.

 

There is a coolant surrounding the reactor which is used to

protect the core from overheating. It absorbs the heat generated

during the fission of Plutonium atoms and circulates it to a heat

exchanger. This heat converts water in the exchanger into

steam, which is used to drive a turbine and generate electricity.

Advantages [30]

  • A breeder reactor creates 30% more fuel

than it consumes. After an initial introduction of

enriched uranium, the reactor only needs infrequent

addition of stable Uranium, which is then converted

into the fuel.

  • It can generate much more energy than

traditional coal power plants. Just 3 grams of uranium, on

undergoing fission, can release ten times the energy

produced by a ton of coal.

  • Breeder reactors can even use the Uranium

waste from other Uranium processing plants and spent

fuel from traditional fission reactors, along with depleted

Uranium from nuclear weapons as fuel.

  • Uranium-235 used by light-water reactors is

rare on Earth, and its reserves are likely to run out

within 100 years. On the other side, Uranium-238 used

by breeder reactors is plentiful; in fact it is as common

as tin. In the US alone, uranium-238 reserves are

expected to last for at least 1,000 years.

  • Fuel prices of breeder reactors will remain

fairly stable because of the abundance of Uranium-238

on Earth.

  • This technology does not contribute to air

pollution, except during the mining and processing of

the Uranium ore.

  • Breeder reactors use a small core, which is

important to sustain chain reactions. Besides, they do not

even need moderators to slow down neutrons, as they use

fast neutrons.

 

Disadvantages [30]

  • Breeder reactors use highly enriched fuels,

which pose the danger of critical accidents. They also

work at a very high temperature and a fast pace.

  • Plutonium persists for a long time in the

environment, with a half-life of 24,000 years, and is

highly toxic, causing lung cancer if even a small amount

is inhaled.

  • Construction and operation are very costly.

Between $4 to $8 billion is required for construction

alone.

  • The byproducts formed during the fission of

Plutonium have to be removed by reprocessing, as they

slow down the neutrons and reduce efficiency. However,

this step of reprocessing produces a very pure strain of

Plutonium, which is ideal for use in nuclear weapons.

This poses a risk, as terrorists may attempt to sabotage

or steal the Plutonium.

  • To date, not a single breeder reactor has proven

economically feasible. Every year, billions of dollars

worldwide are spent for the safe storage of the Plutonium

produced, which is then useless, as few reactors use it as

fuel.

  • In practice, a breeder reactor requires 30

years to produce as much plutonium as it utilizes in its

operation.

  • It requires liquefied sodium or potassium

metal as a coolant, as water would slow down the

neutrons. These metals can cause a mishap, as they react

violently when exposed to water or air.

  • These reactors are complex to operate.

Moreover, even minor malfunctions can cause prolonged

shutdowns. Their repair is tedious and expensive too.

  • Breeder reactors have had several accidents. For

example, in the US, the Experimental Breeder Reactor I

suffered a meltdown in 1955. Similarly, Reactor Fermi I

suffered a partial meltdown in 1966, and was closed down

after a series of sodium explosions. Currently, only

Russia, China, India, and Japan have operational breeder

reactors.

 

So, while breeder reactors are highly efficient in producing

their own fuel, the costs and dangers they pose explain why

most nations choose to avoid them. This is why, US

President Jimmy Carter passed an executive order in 1977,

which banned the reprocessing of nuclear material.

 

  1. HIGH TEMPERATURE GAS COOLED REACTOR –

(HTGR) [31] However, there is a new generation, Generation IV, of nuclear

reactors which combine the benefits of safety with easier

disposal of radioactive materials. The High Temperature Gas

Cooled Reactor (HTGR)] uses a graphite moderator with a

once through Uranium fuel cycle. Its temperature can reach

1000º C. The reactor core can be either a “prismatic block” or

a “pebble-bed,” which is currently being developed in China.

This design takes advantage of the inherent safety

characteristics of a helium cooled graphite moderated core

with specific design optimizations. The graphite has large

thermal inertia and the helium coolant, which is inert, has no

reactivity effects. The graphite core is highly stabile even at

high temperatures.

 

The main features of HTGRs are enhanced safety, high

thermal efficiency, economic competitiveness, and

proliferation resistance and these make this technology a

promising candidate for nuclear power plant deployment [32].

 

One of the driving forces behind the HTGR philosophy is the

manner in which it produces heat. Net thermal efficiencies

greater than 45% can be achieved with some of the designs of

HTGRs. The high outlet gas temperatures may also be utilized

as a heat source in endothermic chemical processes. Examples

include applications in coal chemistry and upgrading of

hydrocarbons. Hydrogen production is another promising field

for deployment of the HTGR. The short construction period,

modularity and low capital cost are also attractive

characteristics of HTGRs. The foremost motivation for the

development of HTGR technology is its enhanced safety

features along with its high temperature capabilities.

 

The enhanced safety of HTGR fuel is due to its coated particle

design known as TRISO. [33] This is a Uranium,

carbon and oxygen mixture consisting of uranium oxide

coated with layers of pyrolytic carbon and silicon carbide.

Coated particles are so designed that they can withstand high

internal gas pressure without releasing any fission products to

the environment. They are also easy to collect for disposal.

 

The reactor uses helium as a coolant instead of water.

After the helium is heated to 750oC (1382oF)

It is sent into a stream generator where it heats water until

It becomes high temperature stream. That stream then flows

into a stream turbine. China’s SNPTC’s project consists

of two.MW high temperature reactor pebble-bed modules

There is also a joint venture with Saudi Arabia for a

seawater desalination project.

The future is on Very High Temperature Reactor – VHTR

operating at 1000oC

 

  1. Thorium Reactors [34]

Since uranium itself will not last more than a couple

of hundred years, a new thorium reactor is being developed,

mostly in India and China, using a more abundant thorium

found on earth – about 500 times greater than

Uranium-235.

 

Thorium has a higher melting point and lower operating

temperature which makes it inherently safer than straight

Uranium and more resistant to core meltdowns.

Thorium itself is fertile but not fissile. That means it is a

material, which is not itself fissile (fissionable by thermal

neutrons), that can be converted into a fissile material by

irradiation in a reactor. There are two basic fertile materials:

Uranium-238 and Thorium-232. When these fertile materials

capture neutrons, they are converted into fissile Plutonium-239

and Uranium-233, respectively.

 

Thorium reactor uses Thorium-232 combined with

Uranium-233 added to the fluoride salts in the core-The

molten salt turns into Liquid Fluoride Thorium Reactors.

LFTR. As fission occurs heat and neutrons are released from

the core and absorbed by the surrounding salt. This runs a heat

exchanger heating an inert gas such as helium which drives a

turbine to generate electricity. At the same time Thorium- 232

transmutes into Uranium-233 which is useful in a variety of

ways.

 

LFTR provides numerous benefits. Any leftover radioactive

waste cannot be used for weaponry. The fuel cost is lower than

that of a solid fuel reactor, it also is 20 % more efficient than a

traditional light-water reactor. Though still experimental,

LFTR may well prove to be the breakthrough solution that

will make nuclear energy an acceptable part of sustainable

green energy production everywhere on Earth.

 

  1. CONCLUSION

Alternative energies are certainly the energy of the future.

However, both solar and wind applications need a large

amount of space, and require high construction and

maintenance costs. Add to this the inevitable down time

when wind or sunlight are absent which makes it

essential to store energy in batteries of various kinds.

 

Only nuclear reactors can provide energy 24 hours a day with

very little down time or maintenance. In spite of high

construction and fuel costs, overall their operation is reliable

and low cost. However the use of radioactive fuels like

Uranium and Plutonium can lead to undesired dangers from

terrorism or the production of nuclear weaponry.

 

The question remains: Will the public accept the benefits

of nuclear energy while recognizing its related possible

ill effects? Or can new developments in science and

engineering reduce these dangers sufficiently to persuade

people around the world that nuclear power can generate

electricity safely?

————————————————————————

About the Author

Gioietta Kuo, MA at Cambridge, PhD in nuclear physics, Atlas

Fellow at St Hilda’s College, Oxford University and Princeton

University Plasma Physics lab, is a research physicist. She has

published over 70 professional articles and over 100 articles on

environmental problems in World Future Society publications and

online at wfs.org, amcips.org, MAHB (Millennium Alliance for

Humanity and Biosphere) Stanford and other worldwide think

tanks. Also in Chinese in ‘ People’s Daily’ and ‘World

Environment’ Magazine of the Chinese Ministry of

Environmental Protection, and others in China. Her website is

www.gioiettakuo.com. She can be reached at

kuopet555@comcast.net.

 

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–//–

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