Why energy efficiency?
Introduction
Energy efficiency is all about making the best use of energy and not wasting it.
Do you ever think about the energy that you use – the depth of your hot bath, the length of your
hot shower or whether the lights really need to be on? Do you pay for your energy? Generally,
we only worry about using energy efficiently when we have to pay for it and if the price is high
enough. In this case, we choose to improve our energy efficiency because the high price of
energy forces us to improve our efficiency.
In some cases, through reading and personal research, people develop an environmental
conscience and choose to improve their energy efficiency because of the negative impact that
energy generation currently has on our planet (acid rain, global warming, disease).
Some cultures have a close relationship with the earth and depend on their immediate
environment for their survival. People from these cultures are usually aware of the need for
energy efficiency (eg the efficient use of firewood) from an early age.
Industry and commercial businesses pay for their energy and the aim of these businesses is to
make a financial profit. Surely then we should expect that industry and commerce would be
using energy as efficiently as possible? Often, the answer is no.
This module introduces the idea of energy efficiency and then goes on to discuss:
 the different forms of energy (energy media) that we find in industry and commercial
businesses and typical measures that can be introduced to improve energy efficiency
 the energy assessment process
 a case study of an energy assessment
For this module, you will be expected to perform an energy assessment of an industry or building
that you have access to. The report that you write will count towards your assessment mark for
this course.
Energy Efficiency
Why should we use energy more efficiently?
1. Because we can save a lot of money.
Often a simple and cheap change to an energy system can save a lot of money. (Covering
your hot water cylinder with an extra layer of cheap insulation (Think-pink or bubble wrap) can
save you 30% to 40% of your monthly water heating costs.) The savings to large industries
can be enormous. South Africa currently has the cheapest electricity in the world but this is
about to change (because funds are required to build more power stations).
2. Because we need to reduce our CO2 emissions and pollution.
South Africa is a major contributor to the problem of global warming because of the CO 2
emissions of our coal-fired power stations. The area around Witbank suffers regularly from
acid rain because of sulphur di-oxide in these emissions. Some trees and crops are
negatively affected by acid rain. Lung and eye irritation (partially from power station
emissions) can occur when people are exposed to particulates and sulphur in the air. Health
problems from exposure to the emissions affects people close to the power stations. Acid
rain can affect neighbouring countries. Global warming and the associated climate changes
affects the whole planet. ESKOM currently does not include the cost of these problems in the
price of electricity and SA has a vast amount of coal that can be cheaply mined - therefore
electricity in SA is cheap but we all end up with the problems associated with coal electricity
generation. We should care how much CO2, SO2, and particulates we cause to be produced.
Task: Type +witbank +”acid rain” into Google and skim over some of the sites.
3. Our addiction to cheap oil has lead to war, poverty and health problems
Petrol and diesel are refined from crude oil which is a non-renewable resource. Oil is
extracted and controlled by powerful multi-national companies. The money from oil has
fueled wars and corruption and has displaced local people (eg the SHELL-Nigeria-Nguni tribe
saga and the ongoing Iraqi conflict).
Task: Type +shell +nigeria +conflict into Google
Emissions from petrol and diesel combustion engines cause health problems in cities and
contribute to global warming.
Task: Type +”mexico city” +smog into Google
We may think it is a good idea to make use of what we’ve got , but in 50 years time we may
find that oil is extremely useful for some other reason. When we look back we may think that
burning it all up in our engines and boilers was a bit foolish (especially since combustion
engines can easily run on plant-derived oil and alcohol and other technologies like battery
electrical storage and fuel cells are well tested). The only problem now is that pressure to
grow fuel oil crops is threatening food security and food prices.
Task: Investigate the website: www.evworld.com
So why do some industries or commercial businesses waste energy?
 To save time.
A study in the USA (De Rosney – The Macroscope) found that theoretically 6x106kcal are
required to manufacture a 1,5 ton motor vehicle. In practice: 32x10 6kcal are being used.
Why? To save time. Manufacturers are using 80% more energy than is necessary in order to
make motor vehicles faster.
 Because energy is unrealistically cheap (for now)
As we have mentioned already ESKOM does not pay compensation for the externalities
(problems like respiratory and eye disease, acid rain and global warming) associated with
producing electricity from coal. Also, SA has a vast amount of coal that can be cheaply mined
– for these two reasons electricity in SA is cheap. Because electricity is cheap, companies
don’t care about trying to use it efficiently.
 Ineffective use of information and management values
Sometimes the technical and engineering staff know that energy is being wasted and know
what can be done to improve efficiency but they do not get support from top and middle
management. Production quantity and quality is often seen by managers to be more
important than efficient use of resources. (Managers like to talk about money and units
produced. Engineers like to talk about kilojoules and kilowatts.) The operators of the
machines often do not have access to energy information and therefore have no indication
that energy needs to be used more efficiently. Energy is often treated by top management as
an overhead, not a production input (like raw materials).
 Lack of accountability
If energy is perceived to be cheap, no one is paid to monitor and report on energy use in the
plant or building. If you don’t measure it, you can’t manage it.
 Management structure.
Often a plant and financial budgets are split into sections based on the different parts of the
production process. Energy provision is seen as a service, and does not receive the budget,
status or manpower that is required to distribute the energy efficiently or to monitor and report
on its use. For example, a budget and manpower is required for the maintenance of
compressed air pipes and for the monitoring and reporting of compressed air use of each
section. Often, a budget for plant-wide improvements requires decisions to be made at
management levels that are far removed from the technical people in the plant.
Energy media
Energy medium – Compressed Air

Compressed air is used to power equipment ranging from hand tools to large fixed equipment
and for controlling plant processes.

A compressor converts electrical energy into potential energy of air under pressure.

It typically accounts for about 10% of total electrical power consumed by industry (ERI).

Cumulative cost of compressed air is:
10% maintenance
15% capital
75% energy (significant savings possible)

Generally, 30% of compressed air is wasted. End users often regard compressed air as a
free resource even though it is an expensive energy medium. 80% - 93% of electrical energy
used by an industrial air compressor is converted into heat (ERI).

Flow of compressed air is measured in cubic feet per minute (cfm) or cubic metres per hr
(m3/hr). There are 35,31 cubic feet in 1cubic metre.

Key areas where energy can be saved are:
 ensure appropriate use (eg. Don’t use high pressure compressed air where
a low pressure fan could be used)
 eliminate misuse (eg cleaning clothes or sweeping with compressed air)
 reduce demand (Can less compressed air do the same job?)
 maintain distribution lines (Fix holes in pipes.)
 generation (Ensure that cool air enters the compressor – use outside air)
 control and monitoring (Once you know how much you’re using then you can
tell whether you are working more efficiently or not.)
Energy medium – Electricity

Generally used for powering electric motors (machines, pumps, fans, compressors), for
lighting and for heating

Industry consumes over half of SA’s total electricity supply.

One third of the total energy used by industry in SA is electricity. (ERI)

Efficiency varies with application (See overhead “Electrical efficiencies”).

Electrical energy is measured in kilowatt-hours (kWh) or megawatt-hours (MWh). One kWh
equals 3,6 megajoules (MJ). Electrical power is measured in kilowatts (kW), megawatts (MW)
or horse power (1hp = 0,746 kW).

Key areas for electrical energy cost saving are:
- power factor correction
- tariff analysis and load shifting
- improving motor efficiency
- improving efficiency of pumping systems
- efficient use of lighting
- efficient electrical heating/cooling systems
Energy medium – Steam

Used for heating, humidifying and process work (pressure to make pistons move)

Has three main advantages as a heat transfer medium:
1. It transfers heat at constant temperature (useful for heat sensitive materials)
2. The temperature of steam is dependant on its pressure (therefore temperature can be
easily controlled).
3. It is compact in terms of heat content per unit volume and it can be conveyed in simple
piping systems.

The production of steam is increasingly being “farmed out” to specialist contractors who
produce steam on site at contracted prices.

Steam supply is measured in tons per hour (1ton = 1000kg). Steam pressure is measured in
bars, kilopascals or pounds per square inch (1bar – 100kPa = 14,5 psi). The energy
contained in a mass of steam is measured in:





Joules, kilojoules or megajoules
British thermal units (1Btu = 1055 J)
Therms (1 therm = 1,055108 J)
Calories (1 calorie = 4,187 J)
Key areas for energy saving are:
 Optimization of steam generation (minimizing flue gas losses and ensuring
efficient blowdown).
 Optimizing steam utilization (minimizing operating pressure, pipe size, pipe
drainage, condensate return, process heat transfer and insulation).
Energy medium – Fuels

Used for heating (boilers and heaters) and for powering engines (eg. petrol and diesel
engines)

Fuels commonly used in SA are liquid petroleum gas (LPG), heavy fuel oil(HFO), paraffin,
petrol, diesel and coal.

Fuels for heating have various pro’s and con’s. Up to now, overall cost of heat production /
unit heat output has usually been the deciding factor when choosing a fuel. (See overhead
“Pro’s and con’s”)
The energy content of some common fuels is tabulated below:

Fuel
Price
Energy content
LPG
R2,43/l
28 MJ/l
HFO
R1,40/l
35-40 MJ/l
Paraffin (Fluiden
1520)
R2,68/l
36 MJ/l
Coal
R?/ton
29 MJ/kg
Key areas for energy cost saving are:
 minimizing heat lost from the stack (chimney)
 optimizing the process heating system (insulation and optimum process heat
transfer)
The energy assessment process (assuming you are a consultant)
1. Get the job!
-Work freelance for an energy efficiency group
-Combine work with further studies
-Initiate your own project in your place of work - but
ensure that you have support from everyone around
you (particularly above you)
-Sell your service for a) a fixed price or b) a
percentage of their savings that you predict and that
an independant party monitors and verifies
3. Go to the plant
-Meet with chief engineer and top management and
discuss your action plan.
-Walk through the facility with someone who knows
everyone and all the plant processes.
get your bearings
-If it's a big plant, meet section heads (record their
names and positions)
- Look out for, and record, energy conservation
opportunities (ECO's)
Return with/to the chief engineer and inform him of
your intended focus areas and give him a rough
savings estimate if possible.
5.Go away, analyse data, write up remaining parts
of assessment report
- See suggested layout (example of contents page)
- State facts only. Don't say or imply that anyone is
not doing their jobs properly - it's not for you to
decide and you may need their support later.
- Show all calculations clearly and reference all
material.
-Send a rough draft to the chief engineer for his
information and for him to check for any glaring
omissions or errors
- Send final draft and request the opportunity to
present the information if this has not already been
arranged
2. Before going to the plant
-If you are not employed by the company, send
out a pre-assessment form to the chief engineer,
to gather data about the facility layout, processes,
energy forms used, major energy-using
equipment, current energy conservation practices,
previous energy studies, energy use and costs,
production trends, water and effluent use and
costs. Also state what you want from them when
you visit the plant.
-Ensure that top management is involved.
-If you are an employee, much of the above
information will be known to you. You may
need approval of upper management to access
energy bills, machine specifications, production
data and previous studies.
- Find out as much about the company as possible
(internet, library, their brosures)
4. Spend more time in the plant
- You may need a few days and nights
- Gather any remaining background data
- Investigate focus areas
- Set up instruments and take measurements
- Ask the right questions - Get answers from the right people
- Look out for more possible ECO's
- Distinguish between housekeeping ECO's,
ECO's that will require major capital expenditure
and ECO's that are essentially for free if the rght
action is taken.
- Be sure to locate reliable contact people before
you leave
6. Present the assessment findings
- succinctly
- with loads of praise and gratitude for everyone
- professionally
- Get feedback on what areas the personnel
would like to focus first (for a focussed M&V
report)
7. Produce a monitoring and verification (M&V) report
- Tell them what they need to measure and how often
- Tell them what instruments they need and where to install them
- Tell them how to present and interpret the measurements and to whom
- The point is for measurements to be taken before and after any improvements are implemented so that
predicted annual savings can be shown to have been achieved
- A management strategy may need to be included in the M&V report to ensure that these savings continue to
be achieved into the future