User:Anmclarke/sandbox

Solar tracker bits

Basic concept bits

Other factors

Clouds

The above models assume uniform likelihood of cloud cover at different times of day or year. In different climate zones cloud cover can vary with seasons, affecting the averaged performance figures described above. Alternatively, for example in an area where cloud cover on average builds up during the day, there can be particular benefits in collecting morning sun.

Atmosphere

The distance that sunlight has to travel through the atmosphere increases as the sun approaches the horizon, as the sunlight has to travel diagonally through the atmosphere. As the path length through the atmosphere increases, the solar intensity reaching the collector decreases. This increasing path length is referred to as the air mass (AM) or air mass coefficient, where AM0 is at the top of the atmosphere, AM1 refers to the direct vertical path down to sea-level with Sun overhead, and AM greater than 1 refers to diagonal paths as the Sun approaches the horizon.

Interestingly, even though the sun may not feel particularly hot in the early mornings or during the winter months, the diagonal path through the atmosphere has a less than expected impact on the solar intensity. Even when the Sun is only 15° above the horizon the solar intensity can be around 60% of its maximum value, around 50% at 10° and 25% at only 5° above the horizon. Therefore trackers can deliver benefit by collecting the significant energy available when the Sun is close to the horizon.

Solar cell efficiency

Main article: Solar cell efficiency

Of course the underlying power conversion efficiency of a photovoltaic cell has a major influence on the end result, regardless of whether tracking is employed or not. Of particular relevance to the benefits of tracking are the following:

Molecular structure

Much research is aimed at developing surface materials to guide the maximum amount of energy down into the cell and minimize reflective losses.

Temperature

Photovoltaic solar cell efficiency decreases with increasing temperature, at the rate of about 0.4%/°C. For example 20% higher efficiency at 10°C in early morning or winter as compared with 60°C in the heat of the day or summer. Therefore trackers can deliver additional benefit by collecting early morning and winter energy when the cells are operating at their highest efficiency.

Summary

Trackers for concentrating collectors must employ high accuracy tracking so as to keep the collector at the focus point.

Trackers for non-concentrating flat-panel do not need high accuracy tracking:

• low power loss: under 10% loss even at 25° misalignment
• reflectance consistent even to around 50° misalignment
• diffuse sunlight contributes 10% independent of orientation, and a larger proportion on cloudy days

The benefits of tracking non-concentrating flat-panel collectors flow from the following:

• power loss degrades rapidly beyond about 30° misalignment
• significant power is available even when the Sun is very close to the horizon, e.g. around 60% of full power at 15° above the horizon, around 50% at 10°, and even 25% at only 5° above the horizon – of particular relevance at high latitudes and/or during the winter months
• photovoltaic panels are around 20% more efficient in the cool of the early mornings as compared with during the heat of the day; similarly more efficient in winter than summer – and to effectively capture early morning and winter sun requires tracking.

HDMI bits

• In ===Cables=== fix: An HDMI cable is usually composed of four shielded twisted pairs, with impedance of the order of 100 Ω, plus several separate conductors.

Ethernet bits

Ethernet over twisted-pair is typically implemented using the following methods:

Comparison of mainstream Ethernet twisted-pair line transmission methods

	notes	unit	10BASE-T	100BASE-TX	1000BASE-T	10GBASE-T
General characteristics
Gross bit rate		Mbit/s	10	100	1000	10 000
Maximum length		m	100	100	100	100
Cable type			4-pair UTP	4-pair UTP	4-pair UTP	4-pair UTP
Half-duplex (CSMA/CD) mode			Yes	Yes	Specified but not used	No
Full-duplex mode			Yes	Yes	Yes	Yes
Line code
Analog symbol rate		Mbaud	20	125	125	625
Coding density		bit/baud	1/2	4/5	2/1	4/1
Line coding method			Manchester code	4B5B over MLT-3	TCM over PAM-5	Tomlinson-Harashima over PAM-16
Line levels			2 (-1, +1)	3 (-1, 0, +1)	5 (-2, -1, 0, +1, +2)	16
Lanes			1	1	4	4
Pairs used / Total pairs			2/4	2/4	4/4	4/4
Minimum pair bandwidth		MHz	>10	>63	>63	>313
Cable
Minimum cable grade			Cat 3	Cat 5	Cat 5	Cat 6a
Minimum specified bandwidth		MHz	16	100	100	500

Technical characteristics of structured cabling categories

	unit	Cat 3	Cat 4	Cat 5	Cat 5e	Cat 6	Cat 6a
Specified to bandwidth	MHz	16	20	100	100	250	500

VERNet (network)

VERNet or Victorian Education and Research Network (VERN) provides optical fibre transmission services, both dark fibre and Wave-division multiplexing (WDM).

VERNet Pty Ltd, which owns and operates the VERN, was formed in 2004. The shareholders are the 9 universities in Victoria and the Australian CSIRO.

See also

• AARNet
• CSIRO
• SP AusNet
• VicTrack
• Wave Division Multiplexing (WDM)

External links

• VERNet
• [1]
• [2]
• [3]
• [4]
• [5]
• [6]
• [7]
• [8]

AARNet bits

Typos and bits to update

• Add link to VERNet page (when created)