The document provides an introduction to renewable energy sources including biomass energy and other non-conventional energy resources such as fuel cells. It defines biomass as organic material from living or recently living organisms that can be used as energy. Biomass includes plants, wood and waste which are converted to energy through direct combustion or indirect processes like digestion to produce biofuel. Other sections classify biomass resources, explain how biomass is a renewable resource, and discuss thermal-chemical and biological conversion methods. The document also provides descriptions of floating drum and fixed dome biogas plants. Finally, it introduces fuel cells as devices that convert chemical energy directly to electrical energy through hydrogen fuel and oxygen reactions.

1. Introduction to renewable energy
(EGRE1230)
Semester 1 AY 2023-2024
Department of Engineering
MIE
Sultanate of Oman
University of Technology and Applied Sciences
1
ENG_CC_PPT Notes_01Sep2020_V01

2. CLO 5 Part A - Biomass Energy
Description:
• Biomass is organic, meaning it is made of material that comes from living organisms, such as plants and
animals.
• The most common biomass materials used for energy are plants, wood, and waste. These are called
biomass feedstock.
• Biomass contains energy first derived from the sun. Plants absorb the sun‘s energy through photosynthesis,
and convert carbon dioxide and water into carbohydrates.
• The energy from these organisms can be transformed into usable energy through direct and indirect means.
Biomass can be burned to create heat (direct), converted into electricity (direct), or processed into biofuel
(indirect).
• Biomass is renewable and does not generate additional CO2 emissions when burned. This makes it a
viable source of sustainable energy in rural areas and can serve to strengthen farming activities in the
respective region. The world is in the process of making organic matter useful for supplying energy – be it for
heat, electricity or mobility.

3. Classification: The biomass resources are classified upon the source of generation
i. Forestry crops & residue
ii. Agricultural crops & residue
iii. Animal residues
iv. Industrial residues
v. Municipal solid waste
vi. Sewage

4. How Biomass is a renewable resource of energy?
i. Waste residues will always exist – in terms of scrap wood, mill residuals and forest resources
ii. Properly managed forests will always have more trees, and we will always have crops and the residual biological matter
from those crops.
4.3 Chemical composition of biomass:
Biomass is carbon based and is composed of a mixture of organic molecules containing hydrogen, usually including atoms
of oxygen, often nitrogen and also small quantities of other atoms, including alkali, alkaline earth and heavy metals. The
chlorophyll which contains magnesium.

5. 4.4 Difference between biomass and fossil fuels:
• The major difference between biomass and fossil fuels is the time scale required for its
generation.
• Biomass takes carbon out of the atmosphere while it is growing, and returns it as it is
burned.
• If it is managed on a sustainable basis, biomass is harvested as part of a constantly
replenished crop.
• This is either during woodland or arboricultural management or coppicing or as part of a
continuous program of replanting with the new growth taking up CO2 from the atmosphere
at the same time as it is released by combustion of the previous harvest.
• This maintains a closed carbon cycle with no net increase in atmospheric CO2 levels

6. Advantages of Biomass
• Biomass used as a fuel reduces need for fossil fuels for the production of heat, steam, and electricity for residential,
industrial and agricultural use.
• Biomass is always available and can be produced as a renewable resource.
• Biomass fuel from agriculture wastes maybe a secondary product that adds value to agricultural crop.
• Growing biomass crops produce oxygen and use up carbon dioxide.
• The use of waste materials reduces landfill disposal and makes more space for everything else.
• Carbon Dioxide which is released when Biomass fuel is burned, is taken in by plants.
• Less money spent on foreign oil.
Disadvantages of Biomass
• Agricultural wastes will not be available if the basic crop is no longer grown.
• Additional work is needed in areas such as harvesting methods.
• Land used for energy crops maybe in demand for other purposes, such as faming, conservation, housing, resort or
agricultural use.
• Some biomass conversion projects are from animal wastes and are relatively small and therefore are limited. •
Research is needed to reduce the costs of production of Biomass based fuels. • In some cases, is a major cause of

7. 4.3 Biofuel
 Biofuels are fuels produced directly or indirectly from organic material including plant
materials and animal waste.
 More advanced and efficient conversion technologies now allow the extraction of biofuels
from materials such as wood, crops and waste material.
 Biofuels can be of solid, liquid or gaseous forms.

8. Solid Biofuel
 Wood briquettes are environmentally friendly sources of heating.
The briquettes are produced from pure sawmill chips and are residue
from production plant.
 Wood pellets are available in 6 mm and 8 mm which are ideal for
both private use and heavy industrial burners.
 Fire wood from carefully selected logs from pine and spruce can be
delivered in boxes or in bags according to customers’ demand.
 Woodchips are small to medium sized pieces of wood formed by
cutting or chipping larger pieces of wood such as trees, branches,
logging residues, stumps, roots, and wood waste.
Wood briquettes
Wood pellets
Woodchips

9. Liquid Biofuel
 Biodiesel can be produced from straight vegetable oil, animal oil/fats, tallow and waste
cooking oil. The process used to convert these oils to Biodiesel is called
transesterification
 Bio-ethanol is produced through fermentation of sugars derived from crops containing
starch, such as corn, wheat, sugar cane, sorghum plants. It is the largest contributor of
total biofuel production. It can be blended with petrol to produce more efficient fuel.
 Bio-alcohol are always produced by the action of micro-organisms and enzymes through
the fermentation of sugars or starches (easiest), or cellulose (which is more difficult). Bio-
alcohol is the combined name for bio-methanol, bio-ethanol, bio-propanol, and bio-
butanol.
They are classified into two forms 1st generation and 2nd generation bio-alcohols.
 1 st generation bio-alcohols are produced from crops which can be used by human for
eating like sugarcane, sugar beets and potatoes.
 2nd generation bio-alcohols are produced from woody stems, branches which are not
used by human for eating

10. Gaseous Biofuel
 Biogas is a type of biofuel that is naturally produced from the decomposition of organic
waste.
 When organic matter, such as food scraps and animal waste, break down in an anaerobic
environment (in the absent of oxygen) they release a blend of gases, primarily methane and
carbon dioxide.
 Because this decomposition happens in an anaerobic environment, the process of
producing biogas is also known as anaerobic digestion.
 Syngas is an abbreviation for synthesis gas, which is a mixture comprising of carbon
monoxide, carbon dioxide, and hydrogen.
 The syngas is produced by gasification of a carbon containing fuel to a gaseous
product that has a heating value.
 Some of the examples of syngas production include gasification of coal emissions, waste
emissions to energy gasification, and steam reforming of coke.
https://www.youtube.com/watch?v=kI7s6IRpOHA

11. 4.4 Energy conversion from Biomass
There are different methods that convert biomass into usable energy. The mostly used two methods
are thermal-chemical method and biological method.
1. THERMAL – CHEMICAL METHOD
 This method is based on the use of heat as a source of biomass conversion.
 They highly developed for dry biomass, especially for straw and wood.
 The steps involved are, combustion and pyrolysis

12.  Natural biomass:
 The combustion of biomass by oxygen from the air, this reaction releases water and carbon
dioxide, and can be used for domestic heat and industrial heat production.
 It is the chemical decomposition of organic (carbon-based) materials through the application
application of heat.
 Pyrolysis:
 This is also the first step in gasification and combustion, occurs in the absence or near absence
absence of oxygen, and it is thus distinct from combustion (burning), which can take place only if
sufficient oxygen is present.
 The rate of pyrolysis increases with temperature.
 In industrial applications the temperatures used are often 430°C or higher, whereas in smaller-
scale operations the temperature may be much lower.
 https://youtu.be/yHWcddUZ35s

13.  It has been used for long time to produce charcoal from wood and coke from coal.
 This method also releases a lean gas mixture of carbon monoxide (CO) and carbon
dioxide (CO2), hydrogen (H2) and light hydrocarbons.
 This gas, low calorific value, can be used to power diesel engines to produce electricity, or
move vehicles.
 The facility in which you make the pyrolysis and gasification of biomass is called gasifiers.
 The poor gas produced can be used directly or can serve as a basis for the synthesis of
methanol, which could replace gasoline to power internal combustion engines.

14.  The gas produced is more versatile and can be used for the same purposes as natural gas.
 It can be burned to produce heat and steam power in the internal combustion engines
and gas turbines to generate electricity.
 It is a fuel of relatively free from impurities and causes less pollution problems when
burned.
Biomass pyrolysis process - YouTube
Thermochemical Conversion of Biomass to Biofuels via
Pyrolysis - YouTube

15. 2. Biological Method
 Fermentation is a metabolic process in which an organism converts a carbohydrate, such as
starch or a sugar, into an alcohol or an acid.
o For example, yeast performs fermentation to obtain energy by converting sugar into
alcohol.
o Bacteria perform fermentation, converting carbohydrates into lactic acid.
 Methane fermentation is a versatile biotechnology capable of converting almost all types of
polymeric materials to methane and carbon dioxide under anaerobic conditions.
 It is typically used for processing wet biomass. In the fermenters or digesters, cellulose is
the substance that breaks down into a gas, which contains about 60% methane and 40%
carbon dioxide.
 This process requires a temperature of 30-35°C.

16. Types of Biogas plants
 Biogas is a fuel which is produced from the breakdown of organic matter.
 This is produced when bacteria decompose organic material such as garbage and sewage,
especially in the absence of oxygen.
 Biogas is a mixture of about 60 percent methane and 40 percent Carbon dioxide. Methane
is the main component of natural gas.
 It is relatively clean burning, colorless, and odorless.
 Biogas can be captured and burned for cooking and heating.
 This is already being done on a large scale in some countries around the world.
 Farms that produce a lot of manure, such as hog and dairy farms, can use biogas
generators to produce methane .

17.  Biogas production has been practiced for more than 30 years.
 widespread adoption has been hampered by inadequacy of information on its production,
and potential benefits, and the prohibitively high costs of earlier designs.
 The different types of Biogas plants based on the type of digesters used in it are as listed
below ,
1. Floating Drum Biogas Plants
2. Fixed Dome Biogas Plants
3. Low-Cost Polyethylene Tube Digester Biogas plants
4. Balloon Plants
5. Earth-pit Plants
6. Fibrocement Plants

18.  Initially, two types of biogas systems were promoted. They are float-drum type (Indian
digester) and fixed dome type (Chinese digester)
 The main features of these systems are:
 an under-ground digester may be made of masonry stones, concrete or a strong
gauge metal sheet
 an inlet pipe with a substrate receptacle
 an outlet pipe for exhausted slurry
 a floating fixed dome for gas collection
 a gas outlet pipe

19. Floating Drum Biogas plant
The basic components of floating chamber biogas plant
are as follows.
 MIXING TANK - present above the ground level,
used to feed the well mixed stock into the digester
tank.
 DIGESTER TANK – The entire tank is below the
ground level. It is a well like structure. It is divided
into two chambers by a partition wall.
 INLET AND OUTLET PIPE - Inlet pipe is to introduce
slurry into the chamber. Outlet pipe into the
overflow tank for removal of spent slurry.
 GAS HOLDER - It is an inverted steel drum resting
above the digester. The drum can move up and
down i.e., float over the digester. The gas holder has
an outlet at the top which could be connected to
gas stoves.
 OVER LOW TANK - present above the ground level,
used for the removal of spent slurry.

20. Working Details
 A mixture with equal quantities of biomass and
water is prepared in the mixing pit or tank. It is
commonly known slurry.
 The prepared slurry is fed into the inlet
chamber of the digester through the inlet pipe.
 The plant is left unused for about two months and
adding more slurry will be stopped.
 During this period, anaerobic fermentation of
biomass takes place in the presence of water and
produces biogas in the digester.
 Biogas being lighter rise up and being collected
in the gas holder. The gas holder now starts
moving up.

21.  The gas holder cannot rise up beyond a certain level. As more and more gas starts
collecting, more pressure begins to be exerted on the slurry.
 The spent slurry is now forced into the outlet chamber from the top of the inlet
chamber.
 When the outlet chamber gets filled with the spent slurry, the excess is forced out through
the outlet pipe into the overflow tank. This is later used as manure for plants.
 The gas valve of the gas outlet is opened to get a supply of biogas.
 Once the production of biogas begins, a continuous supply of gas can be ensured by
regular removal of spent slurry and introduction of fresh slurry.

22. Fixed Dom Biogas plant
The basic components of floating chamber biogas
plant are as follows.
 MIXING TANK - present above the ground
level, used to feed the well mixed stock into the
digester tank.
 INLET CHAMBER - The mixing tank opens at
the bottom into a sloping inlet chamber.
 DIGESTER TANK – The inlet chamber has an
opening at the bottom into the digester which
is a huge tank with a dome like ceiling. The
ceiling of the digester has an outlet with a valve
for the supply of biogas.
 OUTLET CHAMBER – The digester has an
opening at the bottom into an outlet chamber.
 OVERFLOW TANK - The outlet chamber opens
from the top into a small over flow tank.

23. Working Details
 The various forms of biomass are mixed with an
equal quantity of water in the mixing tank. This
forms the slurry.
 The slurry is fed into the digester through the inlet
chamber.
 When the digester is partially filled with the slurry,
the introduction of slurry is stopped and the plant is
left unused for about two months.
 During these two months, anaerobic bacteria present
in the slurry decomposes or ferments the biomass in
the presence of water.
 As a result of anaerobic decomposition, biogas is
formed, which starts collecting in the dome of the
digester.

24. As more and more biogas starts collecting, the pressure
exerted by the biogas forces the spent slurry into the outlet
chamber.
From the outlet chamber, the spent slurry overflows into the
overflow tank.
The spent slurry is manually removed from the overflow tank
and used as manure for plants.
The gas valve connected to a system of pipelines is opened
when a supply of biogas is required.
To obtain a continuous supply of biogas, a functioning plant
can be fed continuously with the prepared slurry.

25. Comparison between Floating and Fixed Drum Biogas
plants

26. Chapter 4 : Part B - Other Non-Conventional Energy Resources
4.8 Fuel Cell: https://www.youtube.com/watch?v=imV_ufIzxPY
• Fuel cell is a device that converts directly the chemical energy stored in gaseous molecules of fuel and oxidant into
electrical energy. When the fuel is hydrogen the only byproducts are pure water and heat.
• The overall process is the reverse of water electrolysis. In electrolysis, an electric current applied to water produces
hydrogen and oxygen, by reversing the process, hydrogen and oxygen are combined to produce electricity and
water.
• The unit fuel cell structure called the membrane electrode assembly (MEA) typically consists of an electrolyte in
contact on its both sides with two electrodes, one negative electrode (anode) and one positive electrode (cathode).
• Fuel is continuously fed to the anode side and oxidant is continuously fed to the cathode side. Fuel cells can vary
from tiny devices producing only a few watts of electricity, right up to large power plants producing megawatts.
• All fuel cells are based around a central design using two electrodes separated by a solid or liquid electrolyte that
carries electrically charged particles between them. A catalyst is often used to speed up the reactions at the
electrode

27. Fuel cell types are generally classified according to the
nature of the electrolyte they use. Each type requires
particular materials and fuels and is suitable for
different applications.
1. Polymer Electrolyte Membrane Fuel Cell (PEM FC)
2. Alkaline Fuel Cell (AFC)
3. Phosphoric Acid Fuel Cell (PAFC)
4. Solid Oxide Fuel Cell (SOFC)
5. Molten Carbonate Fuel Cell – MCFC

31. 4.9 Wave Power
• Wave power is the transport of energy by ocean surface waves, and the capture of that energy to do
useful work – for example, electricity generation, water desalination, or the pumping of water (into
reservoirs).
• A machine able to exploit wave power is generally known as a wave energy converter (WEC).
• Differential warming of the earth causes pressure differences in the atmosphere, which generate
winds.
• As winds move across the surface of open bodies of water, they transfer some of their energy to the
water and create waves.
• As long as the waves propagate slower than the wind speed just above the waves, there is an energy
transfer from the wind to the waves.
• Both air pressure differences between the upwind and the lee side of a wave crest, as well as friction
on the water surface by the wind, making the water to go into the shear stress causes the growth of
the waves.

32. • Wave height is determined by wind speed, the duration of time the wind has been blowing,
fetch (the distance over which the wind excites the waves) and by the depth and topography
of the seafloor (which can focus or disperse the energy of the waves).
• A given wind speed has a matching practical limit over which time or distance will not produce
larger waves. When this limit has been reached the sea is said to be "fully developed".
• In general, larger waves are more powerful but wave power is also determined by wave speed,
wavelength, and water density.
• We can use a variety of different Wave Energy Devices to harness the energy produced by the
oceans waves. The problem lies in that the oscillatory frequency of an ocean wave is relatively
slow and is much less than the hundreds of revolutions per minute required for electric power
generation.
• Then a great variety of wave energy devices and designs are available to convert these slow-
acting, reversing wave forces into the high speed, unidirectional rotation of a generator shaft.

33. Wave Profile Devices:
These are wave energy devices which turn the oscillating height of the ocean‘s surface into mechanical energy.

34. • Most types of wave profile devices float on the surface absorbing the wave energy in all
directions by following the movements of waves at or near the sea surface, just like a float.
• If the physical size of the wave profile device is very small compared to the periodic length of the
wave, this type of wave energy device is called a "point absorber‖.
• If the size of the device is larger or longer than the typical periodic wavelength, it is called a
"linear absorber", but more commonly they are collectively known as "wave attenuators".
• A linear absorber (wave attenuator) floats on the surface of the water. It is tied to the ocean
floor so that it can swing perpendicularly towards the incoming waves. This device is an of long
multi-segment floating/semi-submerged cylindrical structure composed of several sections
connected by hinged joints.
• As the waves pass, the segments move with the waves, but are resisted somewhat by hydraulics.
The movement of the hydraulics pressurizes oil, which is pumped into hydraulic motors that
power electric generators.

35. Oscillating Water Columns:
These are wave energy devices which convert the energy of the waves into air pressure.
• The Oscillating Water Column, (OWC) consist of a partly
submerged hollow chamber fixed directly at the shoreline
which converts wave energy into air pressure.
• The structure used to capture the waves energy could be a
natural cave with a blow hole or a man-made chamber or duct
with a wind turbine generator located at the top well above the
water‘s surface.
• The constant ebbing and flowing motion of the waves forces
the trapped water inside the chamber to oscillate in the vertical
up-down direction.
• The air above the surface of the water is compressed and
decompressed by this movement every cycle. The air is
channeled through a wind turbine generator to produce
electricity

36. Wave Capture Devices:
These are wave energy devices which convert the energy of the waves into potential energy
 A Wave Capture Device also known as an Overtopping
Wave Power Device.
 It is a device that captures the movements of the tides
and waves and converts it into potential energy.
 Wave energy is converted into potential energy by
lifting the water up onto a higher level.
 Sea water is captured and impounded at a height
above sea level creating a low head situation which is
then drained out through a reaction turbine.

37. Advantages
i. No costs for Energy.
ii. No waste products.
iii. Significant amount of energy can be produced.
iv. Low running costs.
v. Helps to reduce reliance on non-renewable
resources.
Disadvantages
i. Variable energy supply
ii. Suitable location, where strong waves occur
required
iii. Could be noisy
iv. Equipment should be strong to stand against
rough weather
v. High initial capital costs
vi. Visual effect if near land, this could affect
tourism as well
vii. Can harm the marine ecosystem
viii.More expensive for the average consumer
compared to energy generated from non-
renewable resource

38. 4.10 Tidal Power
 Tidal power is a form of hydropower that converts the energy of tides into electricity.
 Tidal power has potential for future electricity generation.
 The tide is created by the gravitational effect of the sun and the moon on the earth causing cyclical movement of the
seas.
 Tidal energy is therefore an entirely predictable form of renewable energy.
 Tides are more predictable than wind energy and solar power.
 Tidal energy can be harnessed in two forms.
Tidal Range: Tidal Range is the vertical difference in height between the high tide and the
succeeding low tide.
 Artificial tidal barrages or lagoons may be
constructed to capture the tide.
 Turbines in the barrier or lagoon generate
electricity as the tide floods into the reservoir;
water thus retained can then be released through
turbines, again generating electricity once the tide
outside the barrier has receded.

39. Tidal Stream
Tidal Stream is the flow of water as the tide ebbs and floods, and manifests itself as tidal current.
Tidal Stream devices seek to extract energy from this kinetic movement of water, much as wind
turbines extract energy from the movement of air
The sea currents created by movement of the tides
are often magnified where water is forced to flow
through narrow channels or around headlands. A
tidal generator converts the energy of tidal flows
into electricity. Greater tidal variation and higher
tidal current velocities can dramatically increase the
potential of a site for tidal electricity generation

41. 4.11 Geothermal Energy
• The word geothermal comes from the Greek words geo (earth) and therme (heat).
• So, geothermal energy is heat from within the earth.
• We can use the steam and hot water produced inside the earth to heat buildings or generate
electricity.
• Geothermal energy is a renewable energy source because the water is replenished by rainfall and
the heat is continuously produced inside the earth.
• Energy inside the earth Geothermal energy is generated in the earth's core, about 4,000 miles
below the surface.
• Temperatures hotter than the sun's surface are continuously produced inside the earth by the
slow decay of radioactive particles, a process that happens in all rocks. The earth has a number
of different layers:

42. • The core itself has two layers: a solid iron core and an outer core made of very hot melted rock, called magma.
• The mantle which surrounds the core and is about 1,800 miles thick. It is made up of magma and rock.
• The crust is the outermost layer of the earth, the land that forms the continents and ocean floors. It can be three
to five miles thick under the oceans and 15 to 35 miles thick on the continents.
Deep underground, the rocks and water absorb the
heat from this magma. The temperature of the rocks
and water get hotter and hotter as you go deeper
underground.

43. Sources of Geothermal Energy
• Most geothermal reservoirs are deep underground with no visible clues showing
aboveground.
• Geothermal energy can sometimes find its way to the surface in the form of:
• -Volcanoes
• -Hot springs
• -Geysers.
• Naturally occurring large areas of hydrothermal resources are called geothermal
reservoirs.
• Geologists use different methods to look for geothermal reservoirs.
• Drilling a well and testing the temperature deep underground is the only way to be sure a
geothermal reservoir really exists.

44. Uses of Geothermal Energy:
People around the world use geothermal energy to heat
their homes and to produce electricity by digging deep
wells and pumping the heated underground water or
steam to the surface. Or, we can make use of the stable
temperatures near the surface of the earth to heat and
cool buildings.
Geothermal System Types:
Dry steam plants use steam piped directly from a
geothermal reservoir to turn the generator turbines,
where natural steam erupted from the Earth.

45. Flash steam plants take high pressure hot water from deep inside the Earth and convert it to steam to drive the
generator turbines. When the steam cools, it condenses to water and is injected back into the ground to be used
over and over again. Most geothermal power plants are flash steam plants
Binary cycle power plants transfer the heat from geothermal hot water to
another liquid. The heat causes the second liquid to turn to steam, which
is used to drive a generator turbine

47. 4.12 Ocean thermal energy conversion (OTEC) :
Non-conventional sources are turning out to be significant sources of energy for humanity. With global
warming a certainty, it is imperative that we turn to non-polluting and renewable sources of energy. One
such source of energy is Ocean Thermal Energy Conversion (OTEC).
• Ocean thermal energy conversion is an electricity generation system. Ocean Thermal Energy, also
called Ocean Thermal Energy Conversion (OTEC), refers to using the temperature difference between
the deep parts of the sea, which are cold and the shallow parts of the sea, which are hot, to run a heat
engine and produce useful work.
• The deeper parts of the ocean are cooler because the heat of sunlight cannot penetrate very deep into
the water. Here the efficiency of the system depends on the temperature difference.
• Greater the temperature difference, the greater the efficiency. The temperature difference in the oceans
between the deep and shallow parts is maximum in the tropics, 20o C to 25o C.
• Tropics receive a lot of sunlight which warms the surface of the oceans, increasing the temperature

48. Closed and Open Cycle OTEC plants:
Closed-cycle systems:
Closed-cycle systems use fluid with a low boiling point, such as ammonia, to power a turbine to generate
electricity. Warm surface seawater is pumped through a heat exchanger to vaporize the fluid. The expanding
vapor turns the turbo-generator. Cold water, pumped through a second heat exchanger, condenses the vapor
into a liquid, which is then recycled through the system.

49. Open-cycle systems:
Open-cycle OTEC uses warm surface water directly to make electricity. Placing warm seawater in a low-pressure
container causes it to boil. The expanding steam drives a low pressure turbine attached to an electrical generator. The
The steam, which has left its salt and other contaminants in the low-pressure container, is pure fresh water. It is
condensed into a liquid by exposure to cold temperatures from deep-ocean water. This method produces desalinized
fresh water, suitable for drinking water or irrigation.

50. Advantages of OTEC system:
-Power from OTEC is continuous, renewable, and pollution-free.
-Unlike other forms of solar energy, the output of OTEC shows very little daily or seasonal variation.
-Drawing of warm and cold seawater and returning
-The seawater, close to the thermocline, could be accomplished with minimal environmental impact.