太阳能热利用与技术考试题型
Assignment for solar thermal conversion (No.1)
This problem involves calculations on four surface: (1) vertical west-facing。(2) vertical north-facing。(3) vertical south –facing。and (4) horizontal. The results you will generate are common intermediate calculations in energy-conscious building design. (A vertical east-facing surface is omitted due to symmetry with the corresponding west-facing wall.)
All calculations are to be performed for two dates:
(1)
21 December。(2) 21 June。
and for two times of day:
(a) 10:00。and (b) 13:00 local clock time (not solar time and you need to convert
from local clock time to solar time).
oo E
N, longitude=102.7The location is Kunming of China, latitude=25.01(A)
Calculate the cosine of the incidence angle for each of the four surfaces, at two different times of day, for each of the two dates (altogether 16 calculations)
(B)
Calculate the sunrise/sunset hour (in solar time) on each of the four surfaces for each of
the two dates.
(C)
2) for each of the four surfaces, Calculate the daily total extraterrestrial radiation (in MJ/mfor each of two dates. (Be careful, in your calculations, to use the sunrise/sunset hour on
the surfaces themselves, and be careful to use the correct unit of time and hour angle).
Assignment for Solar Thermal Conversion (No.2)
The knowledge of the tilt and azimuth for a tracking solar collector is often essential in
1.
system design. For example, programming the microprocessor that controls the tracking requires an algorithm for the rate at which the collector must move for each minute of the day and each day of the year. Another example is tracking flat-plate photovoltaic systems. The collector tilt angle depends on time of day and day of year. This is important in the calculation of collectible energy since the collectible diffuse and ground-reflected radiation both depend on collector tilt angle.
For the following tracking modes, derive expressions for both the collector tilt and the
(a)
horizontal east-west axis tracking。
(b)
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horizontal north-south axis tracking。
(c)
polar axis tracking。and
(d)
two-axis tracking.
[Hint: In some instances, a little bit of thinking about the physical picture can save hours
of messy algebra]
2. Buildings are not always oriented towards due south or north, and in such case, it is necessary to do exchange of coordinate systems for designing the overhang of a south-facing window. Here is a practical design: a building is located in Kunming with the south
wall oriented towards 30 west from south. Please
(a)
derive the expression of projected angle of solar rays on the plane perpendicular to
(b)
Supposing the height of the window is h, how to design the overhang that makes the window completely shaded at 13:30 PM (solar time) from 21 May to 21 July of the year, and makes the window completely exposed to the sun from 21 Oct. to 21 Feb.
Assignment for Solar Energy Thermal Conversion (No.:3)
Solar gain through windows is essential to predict thermal performance of a building, and this exercise is concerned with the calculation of solar heat gain through a single or
double glazed window. Assuming the window glass is 3 mm in thickness and its
-1, refractive index n=1.5.
extinction coefficient k=40 m(1)
double-glasses and a through a single-glass solar Derive expressions of transmittance Plot curves of solar transmittance through both single-glass and double-glasses 。windowwindows vs. the incidence angle.
(2)
Calculate the equivalent transmittance for diffuse radiation through both windows. (3)
2. Please plot
The monthly hemispheric radiation on January in Kunming is H=396 MJ/m h(a): solar radiation falling on windows vs. time of the day (representative day)。(b):
solar radiation through a single-glass window。(c) solar radiation through a double-
(4)
Calculate the daily collectible solar radiation on windows and the daily solar heat gain of 2 / 4
the buildings with a single-glass and a double-glasses window
Assignment for Solar Thermal Conversion (No:4)
Design an ideal CPC (2D) with a half acceptance angle -sided vertical flat a
plate absorber (assuming the height of the absorber is a)
1: please plot the full CPC by the use of string method and describe the procedure of drawing such a CPC.
2: present the equations of reflectors
3: if the CPC is truncated with extreme accepted angle,
t t
and accepted energy fraction of incident energy F().
H t
Assignment of Solar thermal conversion (No.5)
1.
Design an ideal two-dimension CPC. The concentrator is west-east aligned with the tilt angle of
the aperture being site latitude. For such device, the projection angle of sunlight on the plane perpendicular to the concentrator axis is a crucial parameter determining whether the direct sunlight is accepted.
(a)
derive the mathematical express of the projection angle of sunlight on the plane perpendicular to
the concentrator axis.
(b)
if the CPC is required to collect direct sunlight for at least 6 h/day in all days of a year, how much the acceptance half-angle of the concentrator should be set?
2.Design an ideal west-east aligned CPC (2 D) with a horizontal flat one-sided absorber and two asymmetric reflectors. This concentrator is designed to operate in Kunming and required to collect direct sunlight for at least 6 h/day in all days of a year.
Designing concentrators with gaps: Homework of Solar thermal
Conversion No.:7
Design a 2D (trough) edge-ray concentrator for a tubular absorber the radius of which is o. The design must incorporate a gap of
35mm. The acceptance half-angle a
15mm between the cylindrical absorber and the closest point of approach of your reflector.
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(a): Design a collector for maximum concentration, that is, with the virtual
(“Ice-cream-cone-shape) absorber approach developed by Winston and discussed in the lecture.
Explicitly write down all reflector equations you employ and how you arrived at them. Present a complete drawing of your collector, at any scale you find convenient (but with 1:1 aspect ratio of the x and y axes). What is the geometric concentration ratio? What are the gap losses (averaged over the acceptance angle)?
Using radiative exchange factors or any method you find convenient, show how you
derive the analytic formula for the gap losses in this design, as a function of the ratio of
gap size to tube radius g/r. Explain each step in your derivation.
(b): Now design a collector for maximum collection efficiency, that is, with the “loss-less gap”design developed by Winston and discussed in the lecture. Explicitly write down all reflector equations you employ and how you arrived at them. Present a complete drawing
of your collector, at any scale you find convenient (but with 1:1 aspect ratio of the x and y axes). What is the geometric concentration ratio?
Assignment 8
1.
下图为某企业生产的AlN-Al选择性涂层的反射光普曲线，根据你的经验判断这些膜层的质量（国标规定：太阳吸收比大于0.86，发射比小于0.08）如何？请你根自己所学知识指出生产工艺可能存在的问题（据厂家说他们共镀了9层）。
阐述真空管生产过程中的排气和镀膜工艺的质量控制要点2.
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