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Artemova E., Chala K.

National University of Food Technologies (Kiev, Ukraine)

Hydropower

 

Hydropower or  water  power  is  power  derived from  the  energy of  falling  water  and  running  water ,  which  may  be  harnessed  for  useful  purposes. Since  ancient  times,  hydropower  has  been  used  for  irrigation and  the  operation  of  various mechanical  devices, such  as  watermills,  sawmills,  textile mills,  dock  cranes,   domestic  lifts,  power  houses  and   paint  making.

Since  the  early  20th  century,  the  term  has  been  used  almost  exclusively  in conjunction  with  the  modern  development of  hydroelectric  power,  which  allowed use  of  distant  energy  sources.  Another  method  used  to  transmit  energy used  a  trompe,  which  produces  compressed  air  from  falling  water.  Compressed air could  then  be  piped  to  power  other  machinery  at  a  distance  from  the  waterfall.

Water's  power  is  manifested  in  hydrology,  by  the  forces  of  water  on   the  riverbed  and  banks  of  a  river. When  a  river  is  in  flood,  it   is  at  its  most  powerful,  and  moves  the  greatest  amount  of  sediment.  This  higher  force results in  the   removal  of  sediment  and  other  material  from the  riverbed  and  banks  of the  river,  locally  causing  erosion,  transport  and,  with  lower  flow,   sedimentation downstream.

Having  fallen  out  of  favor  during  the  late  20th  century  due  to  the  disruptive ecological  and  social effects  of  large impoundments,  hydropower  enjoyed  a revival  by  2013  as  international  institutions  such  as  the  World  Bank   tried  to  find  solutions  to  economic  development which  avoided  adding  substantial amounts  of  carbon  to  the  atmosphere. Broad  categories  include:

·                    Conventional  hydroelectric,  referring  to  hydroelectric  dams.

·                    Run-of-the-river hydroelectricity,  which  captures  the  kinetic  energy  in rivers  or  streams,  without  the  use  of  dams.

·                    Small  hydro  projects  are  10  megawatts  or  less  and  often  have  no artificial  reservoirs.

·                    Micro hydro  projects  provide  a  few  kilowatts  to  a  few  hundred  kilowatts to  isolated  homes,  villages,  or  small  industries.

·                    Conduit  hydroelectricity projects utilize  water  which  has  already  been diverted  for  use  elsewhere;   in  a municipal  water  system  for  example.

·                    Pumped-storage  hydroelectricity  stores  water  pumped  during  periods  of low  demand  to  be  released  for  generation  when  demand  is  high.

The  economics – cost  reduction

Normally,  small-scale  hydro  installations  in  rural  areas  of  developing countries  can  offer  considerable  financial  benefits  to  the  communities  served, particularly  where  careful  planning  identifies  income-generating  uses for  the  power. The  major  cost  of  a  scheme  is  for  site  preparation  and   the capital cost  of  equipment. In  general, unit  cost  decreases  wit a larger  plant  and with  high  heads  of  water. It  could  be  argued  that  small-scale  hydro technology  does  not  bring  with  it  the  advantages  of  ‘economy of scale’,  but many  costs  normally  associated  with  larger  hydro  schemes  have  been ‘designed out’  or  ‘planned out’  of  micro  hydro  systems  to  bring  the  unit  cost  in  line  with  bigger  schemes.

This  includes  such  innovations  as:

• using  run-of-the-river  schemes  where  possible  -  this  does  away  with  the cost  of  an  expensive  dam  for  water  storage

• locally  manufactured  equipment  where  possible  and  appropriate

• use  of  HDPE penstocks  where  appropriate

• electronic  load  controller – allows  the  power  plant  to  be  left   unattended, thereby  reducing  labour  costs,  and  introduce  useful  by – products  such  as  battery  charging  or  water  heating  as  dump  loads  for  surplus  power

• using  existing  infrastructure,  for  example,  a canal  which  serves  an  irrigation  scheme

• siting  of  power  close  to  village  to  avoid  expensive  high  voltage distribution  equipment  such  as  transformers

• using  pumps  as  turbines  (PAT) - in  some  circumstances  standard  pumps can  be used  ‘in reverse’  as  turbines

• using  motors  as  generators  -  as  with  the  PAT  idea,  motors  can  be  run  ‘in reverse’  and  used  as  generators

• use  of  local  materials  for  the  civil  works

• use  of  community  labour

• good  planning  for  a  high  plant  factor  and   well  balanced  load  pattern

In  recent  years  there  has  been  much  debate over  the  appropriate  scale  of hydro power. Many  argue   that  large hydro  is  not  only  environmentally damaging  but  that  there  is  also  a negative  social  impact  where  large imported  technologies  are  used.

 

Literature:

1.     Micro-hydro  power,  Adam Harvey,  2004,  Intermediate  Technology Development  Group.

2.     "Hydroelectric  Power". Water  Encyclopedia.

3.     http://en.wikipedia.org/wiki/Hydropower