Engineering_Utilities_Module_6.pdf.pdf

Module 6
Emerging Sustainable
Technologies
Engr. Gerard Ang
School of EECE

Sustainable Buildings
• Sustainability – it is our ability to meet current needs without
harming the environmental, economic, and societal systems on
which future generations will rely for meeting their needs.
• Sustainable building, also known as a green building – is a
healthier and more resource-efficient structure that is designed,
built, operated, renovated, reused, and eventually
dismantled/demolished in a sustainable manner. It is designed to
meet specific goals such as protecting occupant health;
improving employee productivity; using energy, water, and other
resources efficiently; and reducing the overall impact to the
environment.

Combined Heat and Power
(Cogeneration) Systems
• Cogeneration, also known as combined heat and
power (CHP) – it is the use of a heat engine (or other
means) to simultaneously generate both electricity and
heat. Its principal purpose is to produce electricity but,
as a by-product, the heat produced is used for heating
water, space heating, or industrial process heating.

Combined Heat and Power
(Cogeneration) Systems

Conventional Cogeneration
The basic elements of conventional cogeneration
system are:
1. Prime mover (engine)
2. Generator
3. Heat recovery system,
4. Exhaust system
5. Controls
6. Acoustic enclosure

Stirling Engine Cogeneration
• Stirling engine – it is a closed-cycle, piston-driven,
external heat engine with a gaseous working fluid that
under cooling, compression, heating, and expansion
drives a piston. The working fluid is permanently
sealed within the engine’s system so that no gas
enters or leaves the engine.

Fuel Cell Cogeneration
• Fuel cell – it is an electrochemical
conversion device that directly
converts a fuel into electrical
energy. A hydrogen-oxygen fuel
cell consumes hydrogen and
oxygen and produces water as the
principal by-product

Building CHP Systems
• Building cogeneration
or CHP systems –
produce electrical power
for local buildings, and
use the heat from that
production to also provide
heat to the buildings
(often through
underground steam or hot
water piping systems).

Geothermal Energy Systems
• Geothermal energy – it is thermal energy generated and
stored in the Earth. Earth's geothermal energy originates
from the original formation of the planet, from radioactive
decay of minerals, from volcanic activity, and from solar
energy absorbed at the surface.
• Geothermal power is cost effective, reliable, sustainable,
and environmentally friendly, but has historically been
limited to areas near tectonic plate boundaries. Nut only a
very small fraction may be profitably exploited. Drilling and
exploration for deep resources is very expensive.

• Direct Use of Geothermal Energy
One method used to extract thermal energy from the earth is
referred to as hydrothermal. Hydrothermal energy is manifested
in as hot springs and geysers or through dry steam.
• Geothermal Heat Pump Systems
A geothermal heat pump (GHP), also known as a ground source
heat pump (GSHP), earth-coupled heat pump, or geoexchange
system, is an electrically powered heat pump system that
consists of pipes buried in the shallow ground near the building,
a heat pump, and ductwork in the building.

The fundamental components of a geothermal heat pump
system include the following:
• Ground loop – it is a system of fluid-filled plastic pipes buried
in the ground, or submersed in a body of water, near the
building.
• Heat pump – it is a device that removes heat from the fluid in
the pipes, concentrates it, and transfers it to the building as
heat. For cooling, this process is reversed: heat is transferred
from the building; it is carried in the fluid to the pipes, where it
is transferred into the earth.
• Air delivery system – it is conventional ductwork attached to
the heat pump and used to distribute heated or cooled air
throughout the building.

Biomass
• Biomass – is the term used for all organic material
originating from plants (including algae), trees and crops
and is essentially the collection and storage of the sun’s
energy through photosynthesis.
• Biomass energy – is the conversion of biomass into
useful forms of energy such as heat, electricity and
liquid fuels.

Diagram of
Bioenergy Conversion

Conversion of
Biomass to Bioenergy

Sources of Biomass
• Harvested timber from local forests
• Wood wastes from timber thinning (i.e., wood collected in
forest fire mitigation efforts)
• Residue from paper mills, woodworking shops, and forest
operations (e.g., sawdust, shavings, wood chips, and recycled
untreated wood)
• Agricultural and animal wastes (e.g., manure and litter)
• Food processing (e.g., nutshells, olive pits)
• Garbage from paper, plant, or animal products (e.g., food
scraps, lawn clippings, leaves, wood-based construction
debris), but not made out of glass, plastic, and metals
• Intentionally grown energy crops (e.g., fast-growing native
trees and grasses) and agricultural crops

Types of Biomass Fuels
• Solid Fuels – include timber (logs) and manufactured
logs, wood pellets, briquettes, and corn.
• Liquid Fuels – ethanol (alcohol that is made from any
biomass high in carbohydrates typically corn, through a
fermenting process similar to brewing beer), biodiesel
(combination of methanol with vegetable oil, animal fat,
or recycled cooking greases).
• Gaseous Fuels – methane gas (combustible gas produced
by the anaerobic, or oxygen-free, digestion of vegetable
and/or animal wastes.)

Types of Biomass Technologies
• Direct combustion process – makes use of a furnace or
boiler to convert biomass fuel into hot air, hot water, steam,
and electricity for commercial or industrial uses.
• Anaerobic digestion – is a biochemical process in which
groups of bacteria, working symbiotically, break down
complex organic wastes in animal manure and food-
processing residue to produce biogas, mainly a methane
and carbon dioxide mix.
• Biomass gasification – is a thermochemical process that
converts biomass into a combustible gas called producer
gas that contains carbon monoxide, hydrogen, water vapor,
carbon dioxide, tar vapor, and ash particles.

Types of Biomass Technologies
• Pyrolysis process – very small, low-moisture particles of
biomass fuel are rapidly heated to temperatures in the
range of 450° to 550°C in the absence of oxygen, resulting
in liquid pyrolysis oil, which can be used as a synthetic fuel
oil.
• Fermentation – is the biochemical process that converts
sugars (predominantly from corn) into ethanol.
• Biodiesel production – is a chemical conversion process
that converts oilseed crops into biodiesel fuel.

Photovoltaic
(Solar Electricity) Power
• Solar cell (also called a
photovoltaic cell) – is an
electrical device that converts
the energy of light directly into
electricity by the photovoltaic
effect. It is a form of
photoelectric cell, defined as a
device whose electrical
characteristics, e.g. current,
voltage, or resistance – vary
when exposed to light.

Principle of Operation
of Solar (PV) Cells

Photovoltaic Systems
• Photovoltaic (PV) system – collects solar energy and
converts it to electricity.
• Components of a basic PV System:
1. An array of solar cells that converts sunlight into DC
electricity
2. An inverter that changes DC electricity into AC
electricity
3. A connection to the utility grid for additional power or a
bank of batteries to store collected electricity

Photovoltaic Systems
• Types of PV Systems:
1. Off-Grid PV Systems or autonomous PV systems – they
produce power independently of the utility grid. In
2. Grid-Connected PV System – they interface with the utility
grid.
Stand-Alone Off-Grid
PV Systems
Grid-Connected PV System

Conducting A
Power Load Analysis
The first step in the process of investigating a PV system for a
home or small business is to calculate the power load. A
thorough examination of electricity needs of the building helps
determine:
• The size of the system needed
• How energy needs fluctuate throughout the day and over
the year
• Measures that can be taken to reduce electricity use and
increase the efficiency

Wind Energy Systems
• Winds – are caused by the uneven heating of the
atmosphere by the sun, the irregularities of the earth's
surface, and rotation of the earth. Wind flow patterns are
modified by the earth's terrain, bodies of water, and
vegetative cover. This wind flow, or motion energy, when
"harvested" by modern wind turbines, can be used to
generate electricity.
• Wind power – it is the conversion of wind energy into a
useful form of energy, such as using wind turbines to
make electricity, wind mills for mechanical power, wind
pumps for pumping water or drainage, or sails to propel
ships.

Wind Turbines
Two Types of Wind Turbines:
1. Horizontal Axis Wind Turbine (HAWT) – have the main
rotor shaft and electrical generator at the top of a tower,
and must be pointed into the wind.
2. Vertical Axis Wind Turbine (VAWT) – have the main
rotor shaft arranged vertically. Vertical-axis wind
machines make up just five percent of the wind machines
used today. The typical vertical wind machine stands 100
feet tall and 50 feet wide.

Horizontal Axis Wind Turbines
Horizontal-Axis
Wind Turbines

Vertical Axis Wind Turbines
Darrieus Vertical-Axis
Wind Turbines
Giromills Savonius Vertical-Axis
Wind Turbines

Wind Turbine Components
Conventional horizontal axis turbines can be divided into
three components:
• The rotor component, which is approximately 20% of the
wind turbine cost, includes the blades for converting wind
energy to low speed rotational energy.
• The generator component, which is approximately 34% of
the wind turbine cost, includes the electrical generator, the
control electronics, and most likely a gearbox, for
converting the low speed incoming rotation to high speed
rotation suitable for generating electricity.
• The structural support component, which is approximately
15% of the wind turbine cost, includes the tower and rotor
yaw mechanism.

Total Power of the Windstream
The total power of the windstream is given by:
𝑷𝑻 =
𝟏
𝟐
𝒎𝒗𝟐 =
𝟏
𝟐
𝝆𝑨𝒗𝟑 𝒎 = 𝝆𝑨𝒗
Where:
PT = total power of the windstream, W
m = mass flow rate, kg/s
v = incoming velocity, m/s
ρ = density of air, kg/m^3

Coefficient of Performance
Coefficient of Performance – is defined as the ratio of the
power delivered by the rotor P to the maximum power
available PT.
𝑪𝒑 =
𝑷
𝑷𝑻
=
𝑷
𝟏
𝟐
𝝆𝑨𝒗𝟑
Tip Speed Ratio – is the ratio of the speed of the tip of the
rotor to the wind speed v.
Betz’s Law
According to Betz's law, no turbine can capture more than
16/27 (59.3%) of the kinetic energy in wind. The factor 16/27
(0.593) is known as Betz's coefficient. This was published by
Albert Betz.

Sample Problems
1. The undisturbed wind speed at a location is Vi = 30 mph, the
speed of turbine is 60% of this value and the speed at exit is
40% of Vi. The rotor diameter is 9 m, ρ = 1.293 kg/m^3.
Calculate (a) the power available in undisturbed wind at the
turbine rotor, (b) the power in the wind at outlet, (c) the
power developed by the turbine and (d) the coefficient of
performance.

Solution:
Vi = 30 mi/hr x (1609.34 m/1 mile) x (1 hr/3600 sec)
Vi = 13.42 m/s
A = (π/4)(9)^2 = 63.62 sq. m
(a) Pwind = (1/2)(1.293)(63.62)(0.6)(13.42)^3 = 59,644.58 W
(b) Poutlet = (1/2)(1.293)(63.62)(0.4)(13.42)^3 = 39,763.05 W
(c) Pturbine = 59,644.58 – 39,763.05 = 19,881.63 W
(d) Cp = (19,881.63/59,644.58) x 100% = 33.33%

Sample Problems
2. A 27 mph wind at 14.7 psia and a temperature of 70 deg F
enters a two bladed wind turbine with a diameter of 36 ft.
Calculate (a) the power of the incoming wind (b) the theoretical
maximum power that could be extracted.
Solution:
V = 27 mi/hr x (1,609.34 m/1 mile) x (1 hr/3600 sec) = 12.07 m/s
Pressure = 14.7 psia = 101,325 Pascal
T = 5/9(70 + 460) = 294.44 K
For air, R = 287.058 J/kg-K
ρ = P/(RT) = 101,325/(287.058 x 294.44) = 1.20 kg/m^3
A = (π/4)(36 ft x 0.3048 m/1 ft)^2 = 94.56 sq. m
(a) Pwind = (1/2)(1.20)(94.56)(12.07)^3 = 99.77 kW
(b) Pmax = (16/27) x 99.77 = 59.12 kW

Sample Problems
3. A wind turbine is designed to produce power when the
speed of the generator is at least 905 rpm, which correlates
to a wind speed of 5 m/s. The turbine has a fixed tip speed
ratio of 70% and a sweep diameter of 10 m. Compute the
gear ratio.
Solution:
TSR = rotor speed / wind speed
0.7 = rotor speed / 5
Rotor speed = 3.5 m/s
rotor speed = (3.5 m/s x 60)/(2 x π x 5) = 6.68 rpm
Gear ratio = generator speed / rotor speed
Gear ratio = 905/6.68 = 135.47:1

Power Density of the Windstream
The power density of the windstream is given by:
𝜹 =
𝟏
𝟐
𝝆𝒗𝟑
Where:
δ = power density of the wind, W/m^2
ρ = density of air, kg/m^3
v = incoming velocity, m/s
h = elevation of the wind above sea level, m
T = air temperature, deg C
𝝆 =
𝟑𝟓𝟑
𝑻 + 𝟐𝟕𝟑
𝒆−𝒉/[𝟐𝟗.𝟑 𝑻+𝟐𝟕𝟑 }

Sample Problems
4. The Tehachapi is a desert city in California with an elevation
of about 350 m, and is known for its extensive wind farms.
Compute the power density of the wind when the air
temperature is 30 deg C and the speed of the wind is 12 m/s.
T + 273 = 30 + 273 = 303 K
ρ = (353/303) x exp[-350/(29.3 x 303)] = 1.12 kg/m^3
Power density = (1/2)(1.12)(12)^3 = 967.68 W/m^2
ρ =
353
T + 273
e−h/[29.3 T+273 }
Solution:

Typical Rating of Wind Energy
Conversion Systems
Rated Output Few watts to 2.5 MW
Wind Speed 15 to 35 mph (6.7 to 15 m/s)
Number of Blades 2 to 6
Speed of Rotor at
rated output range
17.5 rpm to 35 rpm for 2 MW
40 rpm to 60 rpm for 40 to 200 kW
Blade Diameters
3.65 m for 1.5 kW
4.88 to 11.58 m for 6 to 40 kW
48.8 to 61 m for 200 kW
91.4 m for 2500 kW 2-blade unit
Rotor Blade Material
Wood for up 10 kW
Aluminum and its alloys for up to 2000 kW
Steel for largest sizes required

Hydropower Systems
• Hydroelectricity – is the term referring to electricity
generated by hydropower; the production of electrical
power through the use of the gravitational force of falling or
flowing water.
• Hydro-power or water power – is power derived from the
energy of falling water and running water, which may be
harnessed for useful purposes.
• Small-scale hydropower systems – generate up to 30
MW
• Micro hydropower systems – generate up to 100 kW
• Pico hydropower systems – generate up to 5 kW

Pumped Storage
Hydropower System

Run-of-the-River
Hydropower Systems

Turbine Output or Developed
Where:
Q = discharge in cu. m/sec for metric system
h = net head of water in meter
η = over-all efficiency of the hydrostation
𝒌𝑾𝒐𝒖𝒕𝒑𝒖𝒕 = 𝟗. 𝟖𝟏𝑸𝒉𝜼
The turbine output in kW from a hydrostation is

Power Developed in a Hydrostation
Energy developed in kW-sec from a hydrostation is
𝑬 = 𝟗. 𝟖𝟏 × 𝑽 × 𝒉 × 𝜼
Where:
V = volume in cu. m
h = net head of water in meter
η = over-all efficiency of the hydrostation

Sample Problems
1. A hydroelectic power plant operates under an effective
head of 50 m and a discharge of 94 m^3/s. Determine the
power developed.
Solution:
Output kW = 9.81Qhη
Assume η = 100%
Output kW = 9.81(94)(50)(1)
Output kW = 46,107 kW

Sample Problems
2. A hydroelectric power station is supplied from a reservoir
having an area of 50 km^2 and a head of 50 m. If the
overall efficiency of the plant be 60%, find the rate at
which the water will fall when the station is generating
30,000 kW.
Solution:
A = 50 km^2 = 50 x 10^6 m^2
P = 9.81Qhη kW
Q = P/[9.81hη] = 30,000/[(9.81(50)(0.60)] = 101.94 m^3 per second
Rate of fall of water level = Q/A = 101.94/(50 x 10^6)
Rate of fall of water level = 2.0388 x 10^-6 m/sec
or (2.04 x 10^-6 m/sec) x (3600 sec/1 hr) x (1000 mm/1 m)
Rate of fall of water level = 7.34 mm per hour

Sample Problems
3. A hydroelectric station has to operate with a mean head of
50 m. It makes use of water collected over a catchment
area of 200 km^2 over which the annual rainfall is 420 cm
with 30% loss due to evaporation. Assuming the turbine
efficiency as 85% and the alternator efficiency as 80%,
calculate the average power that can be generated.

Solution:
V = catchment area x average annual rainfall x (1 – loss due
to evaporation)
V = (200 x 10^6)(4.2)(1 – 0.3) = 588 x 10^6 cu. m
E = 9.81 x V x h x η kW-sec
E = 9.81(588 x 10^6)(50)(0.85)(0.80) = 1.96 x 10^11 kW-sec
E = 1.91 x 10^11 kW-sec x 1 hr/3600 sec = 54.44 x 10^6 kWh
P = 54.44 x 10^6 kWh/(24 hrs/1 day)(365 days/year)
P = 6.21 MW

Rainwater Harvesting
• Rainwater can provide clean, safe, and reliable water so
long as the collection system is properly constructed and
maintained, and the water is treated appropriately for its
intended use.
• Rainwater collection/harvesting systems – intercept and
collect storm water runoff and detain or retain it for later
use. Harvested water can be used for toilet flushing, car
washing, indoor plant watering, pet and livestock watering
or washing, and lawn/garden irrigation.

Design of a Rainwater
Harvesting System
• Factors to be considered:
1. Water Consumption Rate – how much water is needed
and when
2. Amount of Rainfall
3. Rainwater Collected
4. Required Catchment Area
5. Cistern Size
Cistern – it is a waterproof receptacle for holding liquids,
usually water. Cisterns are often built to catch and store
rainwater
6. Gutter/Downspout Size

Rainwater Collected
• The approximated annual rainwater collected (R), is given
by:
𝑹 = 𝟎. 𝟔𝟎 × 𝑨 × 𝒓 × 𝜼
Where:
R = annual rainwater collected in gallons/year
A = catchment area in sq. ft
r = average rainfall for the period under consideration
η = systeml efficiency

Required Catchment Area
• The minimum required catchment area meet a specific
daily rate of consumption is given by:
𝑨𝒎𝒊𝒏 =
𝑸𝒕𝒐𝒕𝒂𝒍 × 𝑫
𝟎. 𝟔𝟎 × 𝒓 × 𝜼
Where:
Amin = minimum required catchment area
Qtotal = daily consumption rate in liters/day
D = number of days in period under consideration
r = average rainfall for the period under consideration
η = systeml efficiency

Cistern Size
• The required cistern storage capacity (ST) can be
approximated by
𝑺𝑻 = 𝑸𝒕𝒐𝒕𝒂𝒍 × 𝑫𝒅𝒓𝒚 𝒔𝒑𝒆𝒍𝒍
Where:
ST = required cistern capacity
Qtotal = daily consumption rate in liters/day
Ddry spell = longest average dry spell in day

Sample Problems
1. A home in Denver, Colorado, has a catchment area
equivalent to the 2400 sq. ft roof footprint (including the
roof overhangs). The home will have 4 occupants and a
water consumption rate of 55 gal per person per day.
Denver Colorado, receives an average rainfall of 15.40
in/year
a. Approximate the rainwater collected over a year.
Assume an efficiency of 85%.
b. Approximate the required cistern storage capacity.
Assume the longest average dry spell will be 4 weeks.
c. Approximate the minimum required catchment area

Solution:
𝑅 = 0.60 × 𝐴 × 𝑟 × 𝜂
𝑹 = 𝟏𝟖, 𝟖𝟒𝟗 𝒈𝒂𝒍𝒍𝒐𝒏𝒔 𝒑𝒆𝒓 𝒚𝒆𝒂𝒓
(a) For the approximated rainwater collected over a year.
Assume an efficiency of 85%
(b) For the approximated required cistern storage capacity.
Assume the longest average dry spell will be 4 weeks
𝑆𝑇 = 𝑄𝑡𝑜𝑡𝑎𝑙 × 𝐷𝑑𝑟𝑦 𝑠𝑝𝑒𝑙𝑙
𝑺𝑻 = 𝟔, 𝟔𝟏𝟔𝟎 𝒈𝒂𝒍𝒍𝒐𝒏𝒔
= 0.60 2,400 15.40 0.85
= 220 4 𝑤𝑒𝑒𝑘𝑠 7 𝑑𝑎𝑦𝑠/𝑤𝑒𝑒𝑘
𝑄𝑡𝑜𝑡𝑎𝑙 = 55 𝑔𝑎𝑙 𝑝𝑒𝑟 𝑝𝑒𝑟𝑠𝑜𝑛 4 𝑝𝑒𝑟𝑠𝑜𝑛𝑠 = 220 𝑔𝑎𝑙𝑙𝑜𝑛𝑠 𝑝𝑒𝑟 𝑑𝑎𝑦

(c) For the approximated minimum required catchment area
𝐴𝑚𝑖𝑛 =
𝑄𝑡𝑜𝑡𝑎𝑙 × 𝐷
0.60 × 𝑟 × 𝜂
𝑄𝑡𝑜𝑡𝑎𝑙 = 220 𝑔𝑎𝑙𝑙𝑜𝑛𝑠 𝑝𝑒𝑟 𝑑𝑎𝑦
=
220 𝑔𝑎𝑙 𝑝𝑒𝑟 𝑑𝑎𝑦 365 𝑑𝑎𝑦𝑠
0.60
𝑔𝑎𝑙
𝑓𝑡2 15.40 0.85
𝑨𝒎𝒊𝒏 = 𝟏𝟎, 𝟐𝟐𝟒. 𝟎𝟗 𝒇𝒕𝟐

Gutter/Downspout Size
• Rainwater captured in the catchment area can be conveyed
to the cistern through gutters and downspouts. Most gutters
come in several sizes and shapes called profiles. These
include a U-shaped trough (a half-round channel shape)
and a K- or ogee-shaped configuration (a front that looks
like the letter K).

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