Water tools

Aeration energy and cost by tariff window

Aeration is usually the largest electricity line of a treatment plant. Map the three load levels onto the day's tariff windows and see where the money goes.

Oxygen through blowers at average loadkg O₂/hFrom the diffused aeration calculator.

Oxygen through blowers at peak loadkg O₂/h

Peak factor (night load = average / factor)

Discharge pressure (gauge)kPa

Inlet absolute pressurekPa

Inlet air temperature°C

Blower efficiency

Night window hours (low load)h

Night tariffper kWh

Morning window hours (average load)h

Morning tariffper kWh

Afternoon window hours (peak load)h

Afternoon tariffper kWh

Evening window hours (average load)h

Evening tariffper kWh

Daily cost

563per day

Yearly cost

205,462per year

Energy per day

6,421kWh/d

Peak window share of cost

46%

Blower shaft power

Power at low load

206kW

Power at average load

268kW

Power at peak load

360kW

How it works

Shaft power at each load from adiabatic compression, with the air mass flow from the oxygen flow and the discharge pressure held constant across loads (which slightly overstates night-time power):

W_{a i r} = \frac{W_{O_{2}}}{0.23} P = \frac{W_{a i r} R T_{i n}}{29.7 n e} [(p_{a b s} / p_{i n})^{n} - 1]

(1)

Cost per window is hours × power × tariff; the day sums the windows and the year multiplies by 365:

C_{d a y} = \sum_{k} h_{k} P_{k} c_{k} E_{d a y} = \sum_{k} h_{k} P_{k}

(2)

where

$W_{a i r}$: air mass flow, kg/s
$W_{O_{2}}$: oxygen through the blowers, kg O₂/h
$P$: blower shaft power, kW
$R$: gas constant, 8.314 J/mol·K
$T_{i n}$: inlet air temperature, K
$n$: polytropic exponent, 0.283
$e$: blower efficiency
$p_{a b s}, p_{i n}$: absolute discharge and inlet pressure, kPa
$h_{k}$: hours in tariff window k
$P_{k}$: power during window k, kW
$c_{k}$: tariff in window k, per kWh

Motor and drive losses are not included: divide by the wire-to-shaft efficiency for metered energy. Currency follows the tariff you enter.

Aeration energy and cost by tariff window

How it works

Related reading