Global question can we fully rely on them?? to

Global warming and depletion of fossil fuels have forced
mankind to look towards alternative sources of energy which can reduces stress
on fossil fuels and our environment, plenty of work has been done to develop
new techniques and methods of electricity generation. Best and easily available
alternative resource are sun, wind and water based energy sources but they are
fluctuating in nature and their intensity is variable in nature so there arise
a question can we fully rely on them?? to meet our demands and can serve in
long term during varying seasons and demand hours, Thus scientists have tried
to answer this problem by developing energy storage technologies like, PV
batteries, Wind batteries, PV or wind based pumped storages and hybrid system
These solutions are competitive to existing conventional system in all aspects.
However, there is another debate rather it is possible to 100% rely and trust
these energy resources for global energy demands, or we can get a major part
from them and meanwhile continue with conventional fossil fuels, to answer this
tough question experts have conducted researches and derived conclusions. As
per a report published in REN21 (United Nations affiliated group)
“70% of world’s energy experts voted in favour of feasibility 100% renewable
energy in all sectors of world which were 19% in 2014, despite the overwhelming
support some were not convinced rather 100% energy supply is possible”.(HERING 2017) This shows that opinion
and understanding is developing in favour of alternative sources of energy and
governments are investing in research and development of them.

100% Renewable Energy 

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Producing 100% renewable energy
have been a main topic of research lately where various leading scientists have
done enormous amount of work to develop the roadmap for this and applied
successfully their theories in different parts of world successfully. “80% decarbonisation
of the US electric grid could be achieved at reasonable cost” (MacDonald,
Clack et al. 2016). Various researchers
developed simulations for 100% renewable energy in various regions that can be
implemented successfully by complementing each other. For example in case of
Australia “A range of 100% renewable energy systems for the NEM are found to be
technically feasible and meet the NEM reliability standard”(Elliston,
Diesendorf et al. 2012). Similar Association
of Engineers (IDA) have developed a road map to move away from its dependence
on fossil and nuclear energy by 2030 which is to support Danish government’s
vision of 100% renewable energy (Lund and Mathiesen 2009). Majority of researchers widely
believe that it is possible to transform world’s energy productions totally on
renewable resources without huge investments and relying on existing
technologies instead we need to change the mindset of masses. We can electrify
all energy sectors and this electricity can solely be provided by 3 means wind,
water and solar (WWS) power(Jacobson, Delucchi et al.). 
This solution is feasible for 139 countries of world along with USA, if
implemented we can get 80% renewable energy till 2030 and 100% by 2050 helping
us to reduce end use by 42.5% and increased access to energy across the world. However,
at the same time many experts have contradictory opinion and resist such
reliance on renewable source they believe it is hard to maintain a balance
between a supply and demand as both are fluctuating in case of renewable
resources of energy. So, matching them both in different parts of world and
time is difficult to achieve in the absence of any base load power station
which can sustain any variations in demand and supply. “A policy prescription
that overpromises on the benefits of relying on a narrower portfolio of
technologies options could be counterproductive, seriously impeding the move to
a cost effective decarbonized energy system. analyses have found that the most
feasible route to a low-carbon energy future is one that adopts a diverse
portfolio of technologies.” (Clack,
Qvist et al. 2017)

Roadmap

To counter the
intermittent nature of wind and sun we can develop mechanisms where a constant
supply is made sure as per demands.

·       Storage

The advantages of
renewable energy could become disadvantage due to volatile nature of primary
source of energy, However, this issue can be handled by developing bigger
energy storage which can capture excess energy during peak production hours and
that energy can be later released during lean periods to balance supply and
demand gap in market, there are many methods to store this energy some are
outlined here.

Mechanical

a)      
Flywheel
energy storage

Flywheel can store
energy by rotation it rotates a rotor at very high speed as it intake energy
and keep energy as rotational energy. When energy is extracted rotor slows down
and release energy to external system. Input and output energy in these wheels
is in the form of electricity. Flywheels with speed ranging from 20,000 to 50,000
rpms have been developed.

b)     
Pumped
water storage

“97% of worldwide
energy storage relies on pump hydro energy storage which is about (155 GW)”(Stocks,
Blakers et al.) In this method surplus energy is utilized
to pump water uphill during peak production hours, later during peak demand
hours that water is released through a turbine to reproduce 80% of consumed
energy.  This is cheaper method with and
more reliable as compared to other alternatives available in markets further to
this it’s easily applicable in countries which have rivers and access to water
easily we can balance the demands with very less damage to environment and the
capacity of storage depend on head of reservoir and catchment area.

c)      
Thermal
Storage

Thermal storage system uses liquid-solid transition of material, when
storage is being done bulk materials will change from solid state to liquid
while releasing reverse will happen. Heat transfer between external environment
and thermal storage is done through a heat transfer fluid, the higher the heat
higher the capacity to store. Sodium hydroxide is taken as good storage fluid,
with high fusion temperature, more temperature stability and lower stream
pressure, it has storage capacity between 120 to 360o C. In another
method we heat bulk materials like (Sodium, molten Salts) heat is stored in
these materials and they don’t change states unlike others and stored heat is
recovered to produce steam which drive turbines for electricity generation.
Water can also be used as storage fluid at very high temperatures ranging above
200o C, this require huge initial investments as we need to create
big cisterns in rocks as containing this much high temperature water in soil is
impossible task. During low demand hours heated water is produced by using
surplus electricity through thermal plants, however while demand surges heat is
retrieved to create steam for turbines to recover required electricity. There
is another commonly available method of energy capturing and utilizing it
during peak demand hours molten salt solar in this heat is captured during day
time and is kept that way before converting it to electricity. This is more
cost effective and efficient as compared to other methods like batteries and
hydro storages. This collected heat is utilized to run a steam based power
generation units’ solar thermal can also be considered more reliable as
baseload as compared to other sources 

http://www.sciencedirect.com/science/article/pii/S1364032107000238

d)     
Batteries

In batteries chemical energy is transformed to electrical energy and
other way round, these can be designed based on required power and capacity few
important factors are life span and depth of discharge. Deep cycle batteries
are suitable for power system which range 17 to 40 MWh with efficiency of 70 to
80%. There is a broad range of batteries depending upon their materials and
methodology of work. Some are mentioned Lead acid battery where positive and
negative electrodes are made of lead dioxide and sponge lead are submerged in
sulfuric acid others are flooded type, Valve regulated, lithium ion. Sodium
sulphur and flow batteries. Large scale batteries are being developed and
integrated in grids successfully all across the world. However, there is a need
to work on cost effective battery system.

http://www.sciencedirect.com/science/article/pii/S0378779608002642

 

e)     
Vehicle
to Grid

Electric vehicles along with hybrid vehicles are mounted with batteries
for storage of energy these batteries can be connected to grid where they get
required energy for propulsion, However, these batteries can be used in other
way around as well where they can become a generation and storage tool as well
during certain periods of day which can help to balance and smooth the operations
by increasing overall capacity of the system. Well integrated system can help
to benefit from batteries when they are parked.

http://www.sciencedirect.com/science/article/pii/S0301421509003978

100% RE models

Denmark has planned
100% renewable energy by 2050, to achieve this they have planned three major
technological changes a) Energy savings be done on demand site b) efficiency
improvements in energy production c) Replacing fossil fuels by renewable energy
and integrating this into system. Two major hurdles in this cause are
intermittent nature of resources and accommodation of transport sector in
system, they did hourly based simulation which was used to design energy system
with ability to balance supply and demand. As per the plan 2030. Renewable
energy will constitute 50% of total energy production and till 2050 100% target
will be achieved which will require a comprehensive socio-economic study and
sensitivity analyses. A projected future forecast is given as below.

 

As per Danish model 100% renewable energy supply is possible but
they have to focus and decide which source to focus from possible options
Biomass and Wind power being to major source making all of this process very
complicated. However, this whole roadmap was developed with creative inputs
from best experts after thorough studies of all aspects of project. http://www.sciencedirect.com/science/article/pii/S0360544208000959

RE for USA and 139 countries

Mark Jacobson and 26 other researchers at Stanford have
crafted a solution of 100% renewable energy for USA and 139 other countries
which require some major steps for transition. They studied the resources
available to each of these countries and developed road map for each depending
on the availability of wind, water, sunlight, and other resources needed to
transfer 80% load on RE source till 2030 and 100% by 2050 along with financial
inputs required for the cause. They believe it is possible by this scenario
however, there are other alternative ways to achieve this goal, in their plan
they also considered local sectors and analysed demands based on industry,
agriculture, transportation etc. Chosen countries emit almost 99% of world’s Co2
and are the ones which have data’s available for study otherwise circle
can be expanded to others as well. They totally relied on wind solar and water,
and did not considered Nuclear. Biogas, clean coal, and Biofuels for their plan
as they emit high amount of pollutions as compared to other sources.
Development and installation of this plan was criticised to be expansive but
Jacobson Stated “Total cost will be one fourth of whole fossil fuel based
system and this system is competent to face seasonal and daily fluctuation
without any failure”.

http://www.cell.com/cms/attachment/2112931975/2084162042/mmc1.pdf

 

Conclusion

Many countries have already achieved major success on
renewable energy front which is a clear indication that renewable energy
without fossil fuel baseload is a reality and is totally reliable. Recently
countries like Iceland, Sweden, Costa Rica have been leading the way in this
cause and have demonstrated practicality of this assumption by their examples.
And some countries have shown a great dedication to task and are investing
heavily to get results in near future which is very positive indicator.
However, despite success there are some concerns which need to be studied and
analysed properly for lasting success of this assumption like it have been
observed by weather data analysis there are patches of periods where both wind
and solar productions can hit bottom line, and economic aspects should be
studied in depth along with social implications of such changes. Forecasting of
future growths in demands of power and response of our RE system should be
studied and predicted very accurately.