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View Full Version : Chatter How renewable energy may be Edison's revenge



Ron Czapala
12-20-2011, 01:07 PM
http://news.yahoo.com/insight-renewable-energy-may-edisons-revenge-111617610.html

LONDON (Reuters) - At the start of the 20th century, inventors Thomas Alva Edison and Nikola Tesla clashed in the "war of the currents." To highlight the dangers of his rival's system, Edison even electrocuted an elephant. The animal died in vain; it was Tesla's system and not Edison's that took off. But today, helped by technological advances and the need to conserve energy, Edison may finally get his revenge.

The American inventor, who made the incandescent light bulb viable for the mass market, also built the world's first electrical distribution system, in New York, using "direct current" electricity. DC's disadvantage was that it couldn't carry power beyond a few blocks. His Serbian-born rival Tesla, who at one stage worked with Edison, figured out how to send "alternating current" through transformers to enable it to step up the voltage for transmission over longer distances.

Edison was a fiercely competitive businessman. Besides staging electrocutions of animals to discredit Tesla's competing system, he proposed AC be used to power the first execution by electric chair.

But his system was less scalable, and it was to prove one of the worst investments made by financier J. Pierpont Morgan. New York's dominant banker installed it in his Madison Avenue home in the late 19th century, only to find it hard to control. It singed his carpets and tapestries.

So from the late 1800s, AC became the accepted form to carry electricity in mains systems. For most of the last century, the power that has reached the sockets in our homes and businesses is alternating current.

Now DC is making a comeback, becoming a promising money-spinner in renewable or high-security energy projects. From data centers to long-distance power lines and backup power supplies, direct current is proving useful in thousands of projects worldwide.

"Everyone says it's going to take at least 50 years," says Peter Asmus, a senior analyst at Boulder, Colorado-based Pike Research, a market research and consulting firm in global clean technology. But "the role of DC will increase, and AC will decrease."

FROM CLOUD TO MICROGRID

The main factor driving demand is the need to conserve energy and produce more of it from renewable sources. Alternating current is generated by rotating engines, but renewable sources such as wind and solar produce DC power. To use it, because of the way our buildings are wired, we first convert it to AC.

Another thing that's happened since Edison's time is the advent of the semiconductor. Semiconductors need DC power, and are increasingly found in household appliances. These have to convert the AC supply back to DC, which is a waste of energy and generates heat. In the early years of industrialization this wasn't an issue, but today it's important, especially in the huge and fast-growing business of cloud computing.

The companies that handle our information traffic are racking their brains to boost efficiency and cut carbon emissions from their plants. Pike Research expects the green data center business to be worth $41 billion annually by 2015, up from $7.5 billion now. That will be just under a third of all spending on data centers.

Finnish information technology company Academica, for instance, has a data center in a granite cave beneath Helsinki's Uspenski cathedral. It uses Baltic sea water to cool the plant and feeds surplus heat to the city's homes. IBM has designed a solar array to power its Bangalore data center. Microsoft has filed a patent application for a wind-powered data center.

Direct current may be one way to increase efficiency and reduce emissions. Right now, outside a handful of universities, it's not the first thing people are thinking of because there are more basic things to do, says Eric Woods, Research Director for Smart Industry at Pike. But for companies on the leading edge, "it's sort of coming out of the research ghetto."

Pike has not put a figure on how big the DC component of the green data center market will be. Swiss-Swedish engineering firm ABB, a big DC advocate, says about 35 percent of demand for green data centers will come from the United States, 30 percent from Europe, and the rest spread globally.

Every day, says ABB, we all send more than 300 billion emails and 250 million tweets globally. The centers to handle all this data are growing by 10 percent each year and already consume 80 million megawatt-hours of energy annually -- almost 1.5 times the amount of electricity used by the whole of New York City. They're also responsible for about 2 percent of global carbon emissions.

DC power could help. At low voltages it has long been used in data centers but will be "game-changing" at higher voltages, ABB says.
Beyond its potential in data centers, DC power's ability to run on renewable energy sources makes it interesting for important plants that need to operate in "island mode" -- independent of the grid -- in case of a supply failure. Building systems with small, self-contained electricity distribution networks known as microgrids is of particular interest to governments and militaries who worry about terrorist attacks.

"In our view the market (for microgrids) is about to take off," said Pike Research's Asmus, who also sees demand for microgrids in countries that aren't densely covered by AC grids, such as Australia and India, and in developing countries looking to replace costly and wasteful diesel generators.

SMART GRIDS

And it's not just "island mode." Thanks to power electronics - semiconductor switching devices - DC can now be transmitted at high voltage over very long distances, longer than AC. It can be easily used in cables, over ground or under the sea.

High voltage direct current (HVDC) systems are the backbone of plans for smart grids, or supergrids, which aim to channel energy from places where power sources such as sunlight and hydropower are abundant to countries where it is scarce.

Siemens, which vies with ABB for market leadership in HVDC transmission, says demand is increasing fast. "By 2020, I'm expecting to see new HVDC transmission lines with a total capacity of 250 gigawatts. That is a dramatic increase," says Udo Niehage, CEO of the Power Transmission Division in Siemens' Energy Sector. "In the last 40 years, we've only installed 100 gigawatts worth of HVDC transmission lines."

Emerging markets have been the main drivers. ABB has installed a 2,000-km line in China that operates DC power; a 2,375-km HVDC project under construction in Brazil will be the world's longest transmission line when it comes online in 2013.

But Europe is also important. HVDC is now used in a power connection between Britain and the Netherlands. The island of Majorca, whose tourists push up power demand every summer, was hooked up to the Spanish mainland in September. The HVDC system can transmit 30 to 40 percent more energy than with conventional overhead lines carrying alternating current.

Jochen Kreusel, the head of ABB's Smart Grid program, says smart grid demand will put Europe at the forefront of HVDC growth over the next 10 years. "At the moment, based on the number of projects, I'm quite sure it's the strongest market," he said. Pike in November 2010 estimated HVDC investment would reach $12.1 billion by 2015.

The bulk of this DC know-how is currently with European companies, although Chinese firms are joining in. Besides ABB, Siemens and France's Alstom are the main players.

NOT THERE YET

There are plenty of obstacles to all these developments. People in some places worry about the environmental damage from laying new grids, others point to a lack of standards and say DC still has technological limitations that need to be fixed.

Public fears about the potential danger of high voltage cables could also be an issue, especially in the United States where standard voltages are already much lower than in Europe. There are practical limitations, such as a shortage of cable-making capacity.

If the economic climate does not improve, cash may also be a constraint. Countries such as Spain and the Netherlands have already cut subsidies to renewable energy projects. ABB's Kreusel says the economic crisis will have an impact on the market, but he still expects DC to become "an evolutionary add-on" to AC grids over the next 20 years.

How would Edison see all this? He might even have foreseen it. "I'd put my money on the sun and solar energy," he reportedly told his associates Henry Ford and

Harvey Firestone in the 1930s. "What a source of power! I hope we don't have to wait until oil and coal run out before we tackle that."

W9GFO
12-20-2011, 01:30 PM
...but renewable sources such as wind and solar produce DC power.

To the best of my knowledge, all rotating generators produce AC*. I think this includes all renewable energy sources except for solar and Peltier type devices.

*Even a PM DC motor when spun makes AC, the commutator switches it so that the output is DC.

Tor
12-20-2011, 01:51 PM
Yep, and in any case it wouldn't make sense to try to send DC from some wind-power station[1] somewhere directly to consumers. When transporting electricity AC is pretty much the only option (because it can be transformed, with all its implications).

Using DC to power a computer room or data center makes sense though, but that's another issue and shouldn't be mixed up with discussions about energy sources.

-Tor
[1] To be clear: They don't generate DC, they generate AC, as was said by the previous poster. I'm merely adding that if they had actually generated DC it wouldn't be useful for consumers even if all the consumer's equipment ran on DC.

SRLM
12-20-2011, 06:05 PM
And on the other end, variable frequency drives (VFDs) are used to power big (elevator size plus) motors by converting the industrial AC to DC, and the back to AC. The DC bridge allows the controller to output any voltage/frequency to the motor, which improves control.

http://www.ece.ualberta.ca/~knight/ee432/ssim/images/figs/cap_dc_link.gif

Heater.
12-20-2011, 08:17 PM
All sounds like gibberish to me.
Surely wind power generators are still producing AC?
Look at many circuits and we see boost or buck converters making higher voltage DC from lower or vice versa but there is AC in the middle.
Perhaps in a data center it is more efficient to have one DC supply for hundreds of servers instead of one per server.
None of that makes Tesla wrong.

Heater.
12-20-2011, 08:22 PM
By the way. AC or DC, Tesla or Eddison, what has any of this got to do with renewable energy?
I have yet to be convinced that there is any such thing as renewable energy.

Bean
12-20-2011, 09:27 PM
The only part of this that makes sense is that there is no easy way to store AC power. A Flywheel is the only way I can think of off-hand.

Bean

W9GFO
12-20-2011, 09:45 PM
The only part of this that makes sense is that there is no easy way to store AC power. A Flywheel is the only way I can think of off-hand.

Bean

You store it in a battery. No matter what electrical energy is stored in it needs to be converted back to electricity - maybe capacitors are the exception.

Ron Czapala
12-20-2011, 10:02 PM
http://en.wikipedia.org/wiki/High-voltage_direct_current

High-voltage direct current
A high-voltage, direct current (HVDC) electric power transmission system uses direct current for the bulk transmission of electrical power, in contrast with the more common alternating current systems. For long-distance transmission, HVDC systems may be less expensive and suffer lower electrical losses. For underwater power cables, HVDC avoids the heavy currents required by the cable capacitance. For shorter distances, the higher cost of DC conversion equipment compared to an AC system may still be warranted, due to other benefits of direct current links. HVDC allows power transmission between unsynchronized AC distribution systems, and can increase system stability by preventing cascading failures from propagating from one part of a wider power transmission grid to another.

The modern form of HVDC transmission uses technology developed extensively in the 1930s in Sweden at ASEA. Early commercial installations included one in the Soviet Union in 1951 between Moscow and Kashira, and a 10–20 MW system between Gotland and mainland Sweden in 1954.[1] The longest HVDC link in the world is currently the Xiangjiaba-Shanghai 2,071 km (1,287 mi) 6400 MW link connecting the Xiangjiaba Dam to Shanghai, in the People's Republic of China.[2] In 2012, the longest HVDC link will be the Rio Madeira link connecting the Amazonas to the São Paulo area where the length of the DC line is over 2,500 km (1,600 mi).[3]


http://www.abb.com/industries/us/9AAF400197.aspx

HVDC (High Voltage Direct Current) and HVDC Light® are systems for transmission of electric power. Both systems are applied to meet special requirements in power grids, and consist of a cable or line for direct current and two (or more) converter stations.

This page will try to explain where HVDC and HVDC Light can be used and what the benefits are.

With a few exceptions, all power lines you see in your surroundings carry alternating current (AC) that oscillates with 50 or 60 cycles per second - whether they are for (extra) high voltage, for medium voltage or for the low voltage distribution grid. These lines form a large interconnected network that ties the power generation plants (coal, gas, nuclear, hydro, wind, etc.) to the consumers.

But where does HVDC come in? It is used to interconnect separate power systems, where traditional alternating current (AC) connections can not be used.
The classical HVDC technique was first introduced in Sweden (Gotland link) in 1954 by ASEA (a founding company of ABB). Today there are over 100 projects in all parts of the world. Typically, a classical HVDC transmission has a power of more than 100 Megawatt (MW) and many are in the 1,000 - 3,000 MW range. There are classical HVDC transmissions that use overhead lines and that use undersea (and underground) cables (or combinations of cables and lines).
HVDC Light® can be called "The invisible power transmission" since it is based on underground cables, although over head lines also are a possibility. It is a fundamentally new power transmission technology developed by ABB in the 1990's. HVDC Light uses underground or submarine cables. The technology extends the economical power range of HVDC transmission down to just a few tens of Megawatts (MW). In the upper range, the technology can reach 1,200 MW and ±320 kV.
In both classical HVDC and HVDC Light it is possible to transmit power in both directions.

Applications for classical HVDC

In summary we find the use for classical HVDC in a power system:

Long undersea cable links (> 50 km)
Long overhead lines (> 600 km)
Interconnection of different grids or networks
Where control of transmitted power is of importance
Combinations of the above
Applications for HVDC Light®

The same applications as for classical HVDC are valid also for HVDC Light, but due to the smaller power rating of HVDC Light, its underground cable technology and its superior controllability, there are many more potential applications than for classical HVDC.

The fact that it is possible to build a long electric power transmission underground and avoid public opposition and long uncertain approval processes, makes the HVDC Light system very attractive. Some of the HVDC Light applications that are in commercial operation are listed here:
Long underground cable link (70 km Gotland HVDC Light) from a wind park (Sweden).
Long underground cable links (59 km Terranora interconnector & 180 km Murraylink) between different grids (Australia)
Undersea cable link (40 km Cross Sound Cable) to Long Island (NY, USA)
Long undersea cable link (70 km Troll A) to feed power to an offshore gas production platform (Norway)
Interconnection of different grids (Eagle Pass)(USA)

One of the characteristics of HVDC Light is its superior ability to stabilize the AC voltage at the terminals. This is particularly important for wind parks, where the variation in wind speed can cause severe voltage fluctuations.

HVDC Light has also the potential of becoming the preferred system for power in feeds to cities, for strengthening of power networks in areas where the public is opposed to new overhead lines, and for evacuation of trapped marginal generation resources where a new extra high voltage AC line would be too costly. But this requires thinking outside the box.





http://www.power-eng.com/articles/2007/10/siemens-to-deliver-hvdc-technology-for-submarine-cable-to-san-francisco.html

Siemens to deliver HVDC technology for submarine cable to San Francisco

10 October 2007 - Siemens Power Transmission and Distribution (PTD) has secured an order to construct a roughly 88-km (53-mile) undersea high voltage direct current (HVDC) transmission link between San Francisco´s City Center electrical power grid and a substation near Pittsburg, California. The order was placed by Trans Bay Cable LLC, based in San Francisco, and a wholly-owned subsidiary of the project developer Babcock & Brown. Siemens´ share of the total order volume amounts to more than $150mn.

From March 2010, the HVDC Plus system will transmit up to 400 MW at a DC voltage of +/- 200-kV and is the first order for Siemens using its innovative HVDC Plus technology. The main advantages of the new HVDC Plus link are the increased network security and reliability due to network upgrade and reduced system losses.

Today, the major electrical supply for the City of San Francisco is coming from the south side of the San Francisco peninsula. The city relies mainly on AC grids which run along the lower part of the bay – with the new HVDC Plus interconnection link power flows directly in the center of San Francisco. In addition to enabling a straight path for energy from the East Bay, the Trans Bay project will decrease the overall transmission grid congestion in that area, increase overall security and reliability of the electrical system.

After commissioning in 2010, the HVDC transmission line will help to meet the City of San Francisco's future electrical demand and is designed to be an energy-efficient, cost-effective solution addressing San Francisco's need for additional transmission capacity. Furthermore, it will reduce the need to build additional new power plants in the City of San Francisco, decrease transmission grid congestion in the East Bay and it will increase the overall security and reliability of the electrical system.

The project will be implemented by a consortium of Siemens and Milan-based Prysmian Energy Cables and Systems. As consortium leader, Siemens was awarded a turnkey contract that comprises the converter stations for the HVDC Plus system, including engineering, design, manufacturing, installation and commissioning of the transmission system. The company will deliver all high voltage components including transformers, converter submodules, converter reactors and breakers and is responsible for the control and protection, civil works and building systems. Furthermore Siemens fulfills all major requirements, which have to be considered for the electrical components as well as for all buildings for a highly seismic zone like San Francisco. The HVDC Plus solution utilizes a minimum amount of space – crucial for converter sites in urban areas – and minimizes environmental impact such as visual implication, audible noise and transport during construction. The consortium partner Prysmian will provide the submarine power cables that will be installed in the San Francisco Bay.

The Trans Bay Cable Project will be the premier installation of Siemens' new HVDC technology, HVDC Plus (Power Link Universal System), an advance in HVDC transmission systems that opens new fields in proven HVDC technology. And with the implementation of voltage-sourced converters (VSC), HVDC Plus is the preferred solution in space-constrained installations. It is ideal for the connection of remote offshore platforms and wind farms to the onshore grid as well as for high-density areas such as San Francisco. HVDC PLUS enhances the performance of the transmission grid, improves reliability and reduces maintenance and assembly requirements.

The heart of the HVDC Plus converter stations is the IGBT (Insulated Gate Bipolar Transistor) based converter where the conversion from AC to DC transmission and reversed takes place. In contrast to line-commutated converter technology, the HVDC Plus system operates with power semiconductors which have turn-on and turn-off capability. The system makes use of the advantages offered by mulilevel voltage-sourced converter technology, which allows connection to very low power systems as well as supplying passive systems, and active and reactive power can be set independently. The capability of very rapid intervention in the power converter for control and protection purposes makes the system highly dynamic, significant for system faults and malfunctions in three-phase systems.

eagletalontim
12-21-2011, 03:17 AM
Yes, Wind Generators produce AC as I am building one myself. The problem with wind generation is you do not have a way to control the speed of the generator reliably so it can be used as AC running at 60hz. This causes the power from the generator to have to be converted into DC, then run through an inverter to turn it back into AC. There is quite a bit of energy wasted through the conversions. If running your house from say a 48 volt system with all DC components, you would be able to store the energy yourself and use much less energy to run the appliances in your house.

Loopy Byteloose
12-21-2011, 04:03 AM
Regarding Bean's comments about using flywheels....
New carbon fiber flywheels have made huge advances in low mass flywheels as a means for energy storage. In fact, they are being considered for automotive use.

I suspect there will continue to be a significant advantage of using AC power for quite sometime. We have a great deal invested in power generation equipment that creates it as it doesn't require complex commutators on the armatures. Yes, solar panels are inclined to produce DC, but Ford has gotten a sterling engine solar power generation system that may be as good or better than a silicon solution. (I keep wondering who is going to wash all those silicon panels and where in a desert do you get the water.)

As always, 'Good' is the enemy of 'the best'. It really isn't about Edison versus Telsa. It is about AC versus DC going head-to-head. Long distance power lines are always going to require high voltage and transformers to bring the voltage down to reasonably safe usage. I have doubts that pulsed DC is going to ever be as efficient as sinusoidal AC.

In any event, we may be going to a 'two grid distribution model'.

Beau Schwabe (Parallax)
12-21-2011, 06:58 AM
W9GFO,

"To the best of my knowledge, all rotating generators produce AC" ... Van de Graaff generators and Wimshurst style machines produce DC.

Tor
12-21-2011, 10:54 AM
All sounds like gibberish to me.
Surely wind power generators are still producing AC?
They do (I don't think any of them use the DC type generators mentioned by Beau). I clarified my own posting just to make sure that it doesn't add to the confusion.

Perhaps in a data center it is more efficient to have one DC supply for hundreds of servers instead of one per server.None of that makes Tesla wrong.
Tesla was right and Edison was wrong. Although there are some ongoing work on transporting DC long distance now (sorry can't find the reference right now), but AC is just so much simpler to handle because it can be transformed.

By the way. AC or DC, Tesla or Eddison, what has any of this got to do with renewable energy?
I have yet to be convinced that there is any such thing as renewable energy.
Energy can't be destroyed and can't be created, so you're right of course. :-)

-Tor

Heater.
12-21-2011, 11:17 AM
From this article: http://www.siemens.com/press/en/pressrelease/?press=/en/pressrelease/2011/power_transmission/ept201101032.htm


...The centerpiece of the HVDC Plus power converter stations is a converter based on IGBT (insulated gate bipolar transistors) which transforms the alternating current into direct-current and back again...... Just recently the world's first HVDC system ....transmits 400 MW of electrical output at a transmission voltage of ±200 kV with low losses and high energy efficiency...

Good grief what on earth are they using for transistors???!!!

I want to see them. No... I want some:)

stamptrol
12-21-2011, 12:18 PM
The first commercial, solid state HVDC station entered operation in 1972 in Eel River, New Brunswick, Canada. Later in the '70's, I worked at the plant doing annual maintenance and it continues to run, tying the power grids of Quebec to those of New Brunswick and the rest of eastern North America.

The thyristors used were from GE and the high voltage required many to be stacked together. The gate firing was through one of the first applications of fibre-optic technology.

In 2011, IEEE recognized the plant as technological milestone: here is part of the note from the IEEE website.



"IEEE to Recognize Eel River High Voltage Direct Current Converter Station as Technology Milestone

24 February 2011 – The world’s first commercial high voltage direct current converter station, located in New Brunswick, Canada, will be recognized as an IEEE Milestone in Electrical Engineering and Computing on 24 February 2011. Built by Canadian General Electric and NB Power, the Eel River converter station offered a reliable and economical way to link adjacent power systems and thereby provide stable power transfers to customers.

Operating since 1972, Eel River was the first converter station designed and built from solid state high voltage, high current silicon solid state thyristors, (solid-state semiconductor devices). The thyristors were triggered through fiber optics, a technology that was still in its infancy at the time.

This technology enabled the Eel River station to convert alternating current generated by Hydro Quebec to direct current, and then back to alternating, providing a smooth transition to NB Power's customers. This capability also enabled NB Power generation to be exported back to New England where energy costs were higher, offering an economic advantage to the parties on both sides of the U.S. border.

Today, the Eel River High Voltage Direct Current Converter Station continues to provide safe and reliable electricity import and export capabilities. During the current Pt Lepreau Refurbishment power outage, NB Power has utilized the facility by purchasing and importing energy via the Eel River converter station. During periods when New Brunswick generation is at a surplus, NB Power or other market participants can export energy into Quebec or further markets tied with Quebec.

The IEEE Milestones in Electrical Engineering and Computing program honors significant technical achievements that occurred at least 25 years ago in technology areas associated with IEEE. To date, more than 100 Milestones have been approved and dedicated around the world.

The dedication is sponsored by the IEEE New Brunswick Section and will be held at Dineen Auditorium, Head Hall, UNB Fredericton Campus in New Brunswick, Canada. IEEE Canada President Om Malik will be one of the featured speakers, along with NB Power representatives. There are currently close to 17,000 IEEE members in Canada."

Cheers,

Tom Sisk

Heater.
12-21-2011, 12:30 PM
stamptrol,

Very impressive. Now I want to see a photo of that stack of thyristors. I find it hard to believe we can switch such huge voltages and so much power with transistors.
Are the picks on this wiki page close to the mark? http://en.wikipedia.org/wiki/Thyristor

Ron Czapala
12-21-2011, 12:49 PM
HVDC electricity transmission
Since modern thyristors can switch power on the scale of megawatts, thyristor valves have become the heart of high-voltage direct current (HVDC) conversion either to or from alternating current. In the realm of this and other very high power applications, both electronically switched (ETT) and light switched (LTT) thyristors[4] are still the primary choice. The valves are arranged in stacks usually suspended from the ceiling of a transmission building called a valve hall. Thyristors are arranged into a Graetz bridge circuit and to avoid harmonics are connected in series to form a 12 pulse converter. Each thyristor is cooled with deionized water, and the entire arrangement becomes one of multiple identical modules forming a layer in a multilayer valve stack called a quadruple valve. Three such stacks are typically hung from the ceiling of the valve building of a long distance transmission facility.

http://en.wikipedia.org/wiki/Manitoba_Hydro

Two of three thyristor valve stacks used for long distance transmission of power from Manitoba Hydro (http://forums.parallax.com/wiki/Manitoba_Hydro) dams

87820

Heater.
12-21-2011, 01:47 PM
Good grief again. Who has the b******s to design, build and test that?

Us hobbyists have trouble enough keeping the smoke in at low voltages and powers:)

Anyway that is thyristors, what's with the IGBTs. Well OK here goes 3300 volts and 1200 amps....http://en.wikipedia.org/wiki/File:IGBT_3300V_1200A_Mitsubishi.jpg

Oh my God!!!

stamptrol
12-21-2011, 04:49 PM
The thyristors were a bit bigger than that picture, but not much. They were a "hockey puck" style that were clamped between heat sink plates. With individual scrs rated at 1500 volts and a few hundred amps, you can appreciate the number required to pass significant power at 13.8 KV (or whatever the converter voltage was; escapes me at the moment.)

There are two complete back-to-back converters each with 4800 thyristors; each converter can pass 160 MW between the 230 KV switchyard and the 138 KV switchyard.

The original installation was air-cooled so was physically quite large (think two medium-sized warehouses), not including 3, 100MW sync condensors for filtering. A possible rebuild would use liquid cooled thyristors.

Cheers,

BobbyV
12-21-2011, 05:41 PM
This thread really reminds me of an interview I had heard of an economist named Jeremy Rifkin. He pointed out how we are really having a hard time getting out of the old school mentality for energy distribution using centralized power generation. For fossil fuel as a source of power it makes sense, but for renewable energy this is a bit silly. Why would I want to use some crazy system that requires several kV DC to distribute "renewable" power to my house, when I could just put solar panels on my roof? As far as I know the sun shines just the same at my house as at a solar farm! The same goes (up to a point) for wind or geothermal energy.

Meeting the energy demands of say, the average American household, would be difficult using local renewable energy but we could always try to use less energy...... for example, perhaps we could, (gasp!) toss out those old 100w incandescents and replace them with CFLs or LEDs. Okay, I'm just being an idealist now, never mind.

Beau Schwabe (Parallax)
12-21-2011, 11:13 PM
It's amazing how much energy we ( the whole planet ) use. I was helping my daughter work on a report dealing with Solar Energy.


Assuming that all all of the energy on the Earth is in some way related or can be directly traced back to Solar, then there is a limit of what we can consume before we start "taking energy from the bucket" faster than it can be put in.

The amount of energy that hits the surface of our planet is about 84 Terra Watts of Energy per day ... that's what's NOT absorbed through the atmosphere.

"We" currently consume 12.5 Terra Watts of energy per day in fossil fuels, wind, solar, etc.

When my daughter was born (9 years ago) "We" consumed about 8 Terra Watts per day of Energy
When I was born (40 some years ago) "We" consumed about 5 Terra Watts per day of Energy

[Gloom and Doom = ON]

If in 30 years our daily consumption increased by only 3 Terra Watts and then recently in 10 years increased by 4.5 Terra Watts, by the year 2059 we could potentially consume more energy than we receive from the Sun. At that point we are "taking energy from the bucket faster than it can be put in."

That's 47 years, and that assumes that the conversion process is 100% efficient (no where close).... We shouldn't be looking for 'alternative energy' forms with the mind set that it will replace our current energy source since it all comes from the same place... What we need to do /and soon/ is figure out how to conserve the energy we have, design with less power requirements, and make sure that our global net consumption stays well under that 84 Terra Watts I mentioned.

[/Gloom and Doom = OFF]


Just my $0.02

W9GFO
12-21-2011, 11:57 PM
84 Terra Watts seems really low. My really quick and rough calculations show about 3,040 Terra Watt hours per day of energy hitting the surface.

Earth's diameter ~ 12,700,000 m

Area exposed to sun = 1/2 dia2 * pi = 126,676,869.774374 sq meters or about 126 trillion sq meters.

About 1,000 watts per sq. meter * 24 hrs = 3,040 trillion Watt hours per day.

Of course, only a small fraction of that is even remotely practical for generating power.

erco
12-22-2011, 12:27 AM
It's amazing how much energy we ( the whole planet ) use.Assuming that all all of the energy on the Earth is in some way related or can be directly traced back to Solar, then there is a limit of what we can consume before we start "taking energy from the bucket" faster than it can be put in.

[/Gloom and Doom = OFF]


Just my $0.02

Silly Beau. Dey ain't nuttin' to worry 'bout as long as we can buy big cheap packs of batteries like this: http://cgi.ebay.com/Fuji-Heavy-Duty-AA-Batteries-%96-60-Pack/400264964791?_trksid=p1468660.m2000036

So just stock up on dem ol' batt-treez and pass me a brewski, Breau!

Beau Schwabe (Parallax)
12-22-2011, 12:49 AM
W9GFO,
Here is a reference I had found. There are also others that correlate similar information.

http://zebu.uoregon.edu/disted/ph162/l4.html


erco,

"silly" - perhaps ... but show me an argument that designing something more energy efficient is a bad thing ... other than it might take longer... the benefit is in the long run.

W9GFO
12-22-2011, 01:02 AM
I believe that reference is in error. Here are some more;

http://en.wikipedia.org/wiki/Sunlight

http://en.wikipedia.org/wiki/Solar_constant

http://en.wikipedia.org/wiki/Solar_energy

http://www.windows2universe.org/earth/climate/sun_radiation_at_earth.html

http://itacanet.org/eng/elec/solar/sun2.pdf

Beau Schwabe (Parallax)
12-22-2011, 01:24 AM
W9GFO,

I agree with those links also... a key phrase is that those measurements are "incident to a plane perpendicular to the rays from the Sun". When your talking about the entire surface where the angle of attack is not perpendicular as well as figuring any albedo effects, the energy per square meter is significantly less when representing the entire surface..

W9GFO
12-22-2011, 01:32 AM
Well sure, but my calculations use the area of the cross section of the Earth, not the actual surface area.

erco
12-22-2011, 03:40 AM
And how long before incandescent bicycle headlights are outlawed? Grab yours now cheap, bound to be a collector's item! And a prize! See end of bikeman's video... http://cgi.ebay.com/Safety-Sports-Light-For-Home%2C-Bike%2C-Camp-CATEYE-HL-330H/280782537494?_trksid=p1468660.m2000037

DavidSmith
12-22-2011, 09:59 PM
I was in energy for 20 years. Phrasing this as carefully as possible: 1) The alternative energy gurus were making a lot of money 2) I never heard a single idea from any of them that hadn't already been thought of (sometimes hundreds of years ago) 3) They sure were good at marketing themselves: One used to claim he attended a VERY famous university and studied high tech (true). What he never mentioned was dropping out.

Renewable energy is like high speed rail. It is always possible to make it sound great (and sometimes it is). But you really don't know until you have looked at the ENTIRE cycle - origin to end. In the case of high speed rail, they always talk about 200 mph. That may be true - station to station. But once you get the whole trip in there - door to door, things change fast. I used to drive from Sacramento, CA, USA to Los Angeles all the time (my mother lived there). I never flew. Flying was only an hour - airport to airport, BUT door to door driving was only an hour longer, I had my own car when I got there, unlimited baggage allowance - you get the picture.

Renewable energy is the way we will have to go, but the current claims all talk about getting the energy. They never mention the 40 or so other things a utility company has to supply: Capacity, load following, reliability, distribution, base load vs load following, etc. For whatever it is worth, I personally believe the (current technologies) alternatives will not be able to compete (dollars AND energy used to get the energy) until efficiency goes up. Solar will not make it until it achieves at least 20% efficiency. I did a study once that showed a just completed PV plant would never pay for itself, even if the solar panels were FREE. The problem? Infrastructure and all the other things conveniently left out of the pro arguments.

I guess I can sum it up as follows: "The sun if free". So is rain, but the bucket to catch it costs.

eagletalontim
12-22-2011, 11:35 PM
I do agree with the above statement, but..... If big corporations made all the energy and sold it to the little people, yes, it will be expensive. If home tinkerers like ourselves build our own energy capturing devices with what we can, we could eliminate some of the load from a main central station. Those that could afford to go big could completely remove themselves from the grid all together which many have already. The initial investment is pretty hefty if you buy all pre-built devices and it still is high if you build it all from scratch, but in the long run, even with maintenance costs, you would still come out cheaper in the long run. I have been working on a wind generator for awhile now which is a fun project. Total cost so far is around $500 for the metal, magnets, and coated copper wire. The grid tied inverter will cost around $800 to $1000. With the way mine is being build, in 5 to 8 MPH wind, I can generate approximately 750 to 800 watts. More can be produces in higher winds until the cut off speed. According to my electric company, I use on average about 2Kw per hour to power my house in the summer. The cost per Kw is .12 where I live. So a 24 hour period costs me roughly $5.76. That is $172.80 for 30 days. By adding the wind generator cost which is approximately $2000 completed and installed, I could removed roughly 700 watts of power for, on average in my area, 10 hours per day. That is 7Kw I would not pull from the power grid bringing my 24 hour cost down to $4.92 a day which for 30 days is $147.60. That is a savings of roughly $25 a month. To pay back the cost of the generator would take 80 months, or about 6 years. By reducing the power used in my house, I could save even more and pay back the original cost faster. Yes, I understand the wind is not always going to be within 5 to 8 MPH every day for 10 hours....it could be higher and it could be lower, BUT, that is $2000 that did not go out to the electric company for roughly 6 years. Then after the 6 years, the rest is money saved. If I went bigger or used other methods, the payoff would not be as fast, but I could go with off grid inverters which are cheaper and be reliant on my own for electricity. The hardest part is the initial cost. After that, it is money saved.