stion $4$:

Imagine an island with local residents and a few tourist resorts that has no nonrenewable electricity supply and requires $500$ kW during $6$ am to $9$ am$,12$ pm

to $2$ pm and $6$ pm to $11$ pm$.$ For the rest of the day $250$ kW of power is

adequate. All appliances work with $240$ VAC and consume a maximum of $10$ A

each. There are three renewable energy resources that can be practically

implemented. It is decided to design a hybrid system that consists of wind

turbines, micro$-$hydro and photovoltaic systems. The specifications of each

system to be integrated are:

$$X$$ number of small horizontal axis wind turbines each with a blade

diameter of $8\mathrm{.}5$ m and a power coefficient of $0\mathrm{.}4,$ gearbox efficiency of

$0\mathrm{.}8$ and generator efficiency of $0\mathrm{.}9.$ Assume an average wind speed of

$10$ m$/$s blowing $8$ hours a day mostly from $6$ pm to $2$ am$.$ The air density

is $1\mathrm{.}225$ kg$/$m$3$

$.$

$$Y$$ number of micro$-$turbines each having a continuous water flow rate

of $100$ litres per second located in a valley $100$ meters below a dam.

The overall efficiency of each micro$-$turbine is $15\%.$ Assume g $=10$ m$/$s$2$

and that the water density is $1000$ kg$/$m$3$

$.$

$$Z$$ number of polycrystalline $250$ W photovoltaic panels connected to a

solar PV system with a system efficiency of $80\%.$ Assume $6$ hours of

operation each day on average from $10$ am to $4$ pm at the system$$s best

performance.

$($a$)$ Carry out a feasibility study and preliminary techno$-$economical analysis and

suggest the optimum hybrid configuration $($X$+$Y$+$Z$),$ size, number, schedule

and contribution of each system to the island total power demand $($base

load and peak fluctuations$).$ To minimise the capital expenditure, the

intention is to employ no or minimum battery bank capacity and have no

part$-$load operation. The levelised costs $($$$/$MWh$)$ for wind, micro$-$hydro, and

photovoltaic systems including batteries & inverters can be taken

respectively as $60,130,$ and $80.$ The capital investment for installation is

$$4,000/$kW for Wind, $$10,000/$kW for Micro$-$hydro, and $$2,000/$kW for PV

energy systems. The power factor is assumed to be unity.

$($b$)$ Draw a flow chart showing the sequence of operation of such hybrid system

with battery storage in a typical day. List all of the assumptions you make$\mathrm{.}4$