PRACTICAL -9
AIM: TO STUDY
OF ENERGY CONSERVATION BY DEMAND SIDE MANAGEMENT
Power station
will use energy in form of coal, oil, gas, uranium etc. This energy is supplied
in bulk and stored within the plant to meet energy need for a week or fornight
or month. Daily or hourly rate of use of energy is not important to supplier or
user (power station).
The picture is entirely different when
supply and demand of electricity comes. Electricity supply has to match demand
at every instant of time. There is no storage of electricity anywhere in
generation, transmission lines & distribution. Present cost of erecting
generating plant, transmission lines & distribution lines is around Rs. 7
crore/MW to 8 crore/MW. So it is essential to use this capacity to the best
possible extent.
The scope for conservation of commercial
energy in india is vast. Demand Side Management (DSM) is an alternative way of
saving energy use by existing consumers. Every MW that is saved from the
existing load is free to be delivered to new customers. Aim os DSM is to reduce
energy consumption without affecting the level of services.
Important
terms
(1)Load Curves: The curveshowing
the variation of load on the power station with reference to time is known as a
load curve.
(2)Maximum
Demand:
It is the greatest demand of load on the power station during a given period.
The load on the power station varies
from time to time. The maximum of all the demands that have occurred during a
given period is the maximum demand. Higher plant demand (i.e. consumer’s
maximum demand) for even one half hour during the month would entail paying
higher demand charges. The peak load on
the GEB system occures between 7.00 a.m. to 11.00 am hours in the morning and
5.00 p.m. to 9.00 p.m. hours and the evening. The GEBV offers disincentive for
consumption during peak hours and concessions for consumption during off-peak
hours. All these measures are taken to control maximum demand. This helps the
supply utility in maintaining an assured and reliable supply without adhoc load
shedding.
(3)Load
Factor: the load factor is the ratio of the average demand of the plant to its
maximum demand for a particular period. The load factor may be daily load
factor, monthly load factor or annual load factor if the period considered is a
day or month or year.
No. of Units supplied in a year
Annual
Load Factor (L.F.) = -------------------------------
Maximum demand*8760
Average load
L.F%=----------------------- *
100
Maximum Demand
Load
factor is always less than 1 because average load is smaller than the maximum
demand. The load factor plays key role in determining the overall cost per unit
generated. Higher the load factor of the power station, lesser will be the cost
per unit generated. In most cases, load factor can be improved by controlling
maximum demand.
Load
factor is always less than 1 because average load is smaller than the maximum demand.
The load factor plays key role in determining the overall cost per unit
generated. Higher the load factor of the power station, lesser will be the cost
per unit generated. In most cases, load factor can be improved by controlling
maximum demand.
Table:
1 Load factor of some industries
Type
of industry
|
Load
Factor (%)
|
Textile,
spinning
Resins
and paint
Engineering
Chemical
amnd Pharmaceutical
Engineering(Cooper,Brass)
Vanaspati
Engineering
(Electrical appliances)
Inorganic
Chemicals
Organic
Chemicals
|
72
to 95
41
to 52
47
to 72
56
to 78
45
to 54
46
to 80
28
to 41
64
to 77
52
to 79
|
Methodes
of controlling Maximum Demand
The
following are the methods to control the maximum demand.
(i)Scheduling
of major loads,
(ii)Storage
of energy during off-peak periods.
(iii)Power
factor control.
(iv)Utility
side control.
(i)Scheduling
of major loads: To remain a record of the maximum demand is the first step to
control the maximum demand. Teke readings every haif hour for a month. The
analysis of readings may indicate the demand is much higher than average demand
of the day during one or two short periods. These periods of high demand may be
due to starting of a major machine.
Then, proper rescheduling of loads
can be tried to reduce the maximum demand.if it is not possible to stop the
machine for a short time, then unnecessary auxiliary machines could be switched
off. It is possible to control the maximum demand directly in some industries
by installing on- line demand management ystems (electronil maximum demand
controller or sophisticated microprocessor based syatems). These systems are
programmed to switch off non-essential loads.when predetermined demand is
likely to be exceeded. Simple system audible/visual alarms, while sophisticated
systems provide a variety of options.
This instruments are beging used in India
on a limited scsle. With more sevear energy crisis.spiraling demand in india
charges will force industries to go for load monitoring and management.
(ii)Storage
of energy during off-peak periods: Maximum demand meter can be effectively used
for demand side management to reduce the peak load requirements by flattening
the load curve cosumers need to be motivated by making themm avare of the
economic benefits of changing over to off-peak category. Off-peak hours could
be used to store semi=processed materials which can be used or processed during
peak hours. For example, chilled water or ice can be proceed at night and used
during the day time for cooling applications. In process plant,lifting of water
to tank or lifting of raw materials to tank to cahnging chilled water
temperature low could possible during off-peak hours.
(iii)Power
factor control: Most of the electricity boards use maximum demand in kVA (not
kW) for billing purposes.
Laod (kW)
Demand
(kVA) = --------------------------
Power Factor
(cosφ)
If
demand load is 800 kW and p.f. is 0.8, the demand is (800/0.8) = 1000 kVA. If
power factor is improved to near unity, kVA demand will became 800 kVA, so 200
kVA demand charges will be saved. Fro p.f. improvement ,capacitors of 60 kVAr
required with investment of Rs. 2.0 lacs. The payback period is likely to be 10
months.
Therefore, demand in kVA is
controlled by improving power factor. So it is prudent to keep the power factor
as close to unity as possible. In spite of the heavy penalties being imposed,
there are number of high Tension industries in Gujarat who care working at
power factors in the vicinity of 0.6.
(iv)Utility
side control : Additional generating capacities to meet demand require
expensive capital and clearences from various authorities like environmental
agencies. Government regulations in some countries require that all demand
management options are examined before new capacities are sactioned. Many
utilities are finding demand management to be a cheaper option. Some important
components of demand side managemant programs are
a)
Information
and guidence to consumers through publications seminars etc.
b)
Free
or subsidiezed energy audits.
c)
Promoting
energy efficient equipmemts though rebates soft loand and proper information
d)
Promoting
co generation and alternative sources of energy.
e)
In
India, fixation of the tariff supplied to the different categories of
consumewrs is influenced by consumer lobbies and politicians for electoral
gains. The tariff system needs restructuring. There are two strategies.
·
Time-of
day metering (different teriffs for peak and off-peak hours)
·
Tariff
based on total energy.
