Q1.

 

1. i) o aid analysis of the variation in flow in a river, a Flow Duration Curve (FDC) is used. Sketch a typical Flow Duration Curve and, with reference to the sketch, describe what Q70 represents.
   1. A rectangular weir has a notch length of 2.5 m, and the water depth is 15 cm.  Using  the  formula ???????? = 1.8????????(???????? − 0.2ℎ)ℎ^1.5 calculate  the  flow  under these conditions, expressing your answer in litres/s.

 

 

 

 

 

 

 

 

 

1. For the energy analysis of a hydroelectric resource given in able Q1a) below, perform the necessary calculations to determine the electrical output power and the energy per 10% of the year for the Q20 and Q70 time periods. Hence calculate the total energy produced by this scheme per year, and state the rated output power of the generating set.

Note - the power values should be given to the nearest whole number in kW, and the energy values should be rounded to the nearest 100 kWh.

	m3/s	m	%	kW	kWh
% of year	Useable flow	Net head	otal efficienc y	Power out	Energy/ 10% period
10	1.62	23	66	241	211,300
20	1.62	26	66
30	1.32	26	67	226	197,600
40	0.95	26	65	157	138,000
50	0.68	26	62	108	94,200
60	0.46	27	58	71	61,900
70	0.30	27	56
80	0.16	27	43	18	16,000
90	0.00	27	22	0	0

 

able Q1a

 

 

 

1. i)     For the renewable based generation scheme given below, describe the grid connection options that would be available for that scheme. Include

a sketch of a block diagram of the connection options. Also discuss the key design considerations for the connection in respect of the main equipment required, and the protection scheme required, i.e. EREC G83, or G59 simple, or G59 full.

Scheme details - a 2 kW PV installation.

 

 

1. Discuss the concept of "Fault Level contribution" from renewable generation systems which are grid connected. Include discussion on why knowledge of the Fault Level on a power system is necessary at any time, and why it is particularly important when new generation is added to the existing distribution network.  

 

Q2

1. A historic building in Callander has stone walls 400mm thick (1.6 W/mK) with plasterboard on the inner surface of 10mm thickness (0.16 W/mK) and an external layer of lime render (0.2 W/mK) 8mm thick. Assuming an internal resistance factor of 0.12 m2 K/W and an external of 0.1 m2 K/W calculate the U value forthis wall.

 

1. A modern low-carbon home is 10m long, 6m wide and 5m high, with a net wall area of 120m2 (U-value = 0.2 W/m2 K), assuming an area of 40m2 of windows and doors (U-value of 0.89 W/m2 K in both cases). he floor (0.2 W/m2K) and roof (0.15W/m2K) are both 60m2. he house has an internal volume of 288m3 and an effective ACH value of 0.8. It receives 5,500 kWh's a year of useful gains (solar and casual gains) per year. Calculate:
   1. he DSHL for the property.                                                                                 
   2. he annual heating demand with a DD value of 2420.                                
   3. he maximum heating demand under a -5°C outside temperature and a 20°C internal temperature (excluding gains).                                                           

If the home is heated by a wood burning stove (90% efficiency), with an CV of 2.4 MWh/ton and a cost of £120/ton, what is the annual wood consumption and cost.

1.                                                                                                                                  

 

DSHL = [∑(UA) + 0.33 NV)]

Building heat loss = DSHL x DD x 24/(1 x 103)

 

 

 

 

 

1.  A brewery, installing a CHP plant, intends to consume 60 tonnes a year of wood fibres, transported by truck. Assume a 44 ton lorry can carry 28.5 tonnes. Assume 5 wood deliveries per year. he load is carried a distance of 85 km's, fully loaded the truck consumes 0.376 l/km and 0.231 l/km when it returns empty.

Estimate the load fraction, the fuel consumption in litres and the energy use if Diesel has a calorific value of 46 MJ/kg and a density of 0.803 lg/l.                               

 

f .l

 

Fc = F     ´ 0.874´[1+ (0.36´

 

(Lf- 50)/100) ]

 

Where

Fc = fuel consumption ( l/km) F f.l= full load consumption

Lf = percentage load fraction

 

Q3.

1. A householder in a remote off grid location in Scotland wishes to go 100% renewable. He plans on using either a wind turbine or PV array alone or perhaps a hybrid of the two combined with a battery. Based on the maximum required daily output to load of 4.25 kWh, for 3 days autonomy and a maximum allowable DoD of 50%, for a 12 V system, calculate the required battery capacity in Ah.

 

1. Briefly explain the key factors that should be considered in relation to battery sizing. Will battery capacity vary based on discharge rate? And if so why? List the three main types of suitable deep-cycle batteries.

 

1. A 60 kW wind turbine has a cut in wind speed of 3 m/s, and an output power characteristic defined by the equation:

P = -0.106v3 + 2.3v2 - 7.6v + 4.5

 

Where P is the power output in kW, and v is the wind speed.

 

 

 

 

 

 

 

he local measured average annual wind speed at 10m above ground level is

4.8 m/s. he turbine is mounted on a 23m tower. From consideration of the local topography, a Hellman coefficient of 0.24 is deemed appropriate for wind speed correction.

 

1. Calculate to 1 decimal place, the average annual wind speed at the turbine hub height   

 

1. It is proposed to install a turbine similar to the above unit at a site 1,200m above sea level to help power a mountain lodge in Iceland, where the average air temperature is -5°C at this location (during the winter season). Using the appropriate equations, determine the average air density for this location:

 

 

Pressure, P = 101325 x ( 1- 2.25577 x 10-5 x height)5.25588

 

 

 

Mair  = 28.97 kg/k.mol,     R = 8.314 kJ/kg.K

 

If the average wind speed for the proposed site, in respect of power Generation, can be taken as 7.5 m/s, calculate the average power output for this location.            
 

T