# Tag Info

15

Your equation is partly correct. You've calculated the energy per photon ($\hbar \nu$), but you've neglected the number of photons. That's why the units don't match (power is energy per unit time, while you've only got energy for each photon). The ideal power (energy per unit time) depends on the area of the solar panel, $A_p$, the number of photons ...

15

There are no silver bullets when it comes to decarbonising the grid. That's good news: it means you can stop looking for one, and accept that every form of generation has its pros and cons. Concentrated solar power [CSP] relies on direct sunlight. Not just ambient daylight, but lots and lots of direct sunlight all year round. Whereas ordinary photovoltaics [...

10

Yes, there are indeed combined PV-T (photovoltaic-thermal) hybrid panels that turn some of the incident light into electricity, and have a circulating fluid and heat exchanger to put some of the heat into a heat store. There's very little take-up of them, because they're just not economic in most circumstances. The theory looks great: PV panels are more ...

10

Yes, increasing the illumination on a solar cell by using lenses or mirrors increases the electric power output. However, there are limiting factors. The efficiency of a solar cell goes down with temperature. The current stays roughly proportional to the photon flux, but the open circuit voltage goes down as the semiconductor junction is heated. Still, ...

10

Everything we do as humans has consequences of some sort. Although not a huge downside (in my opinion), critics have often cited the plant's supposed adverse effects on wildlife: Wikipedia Article: It has been noted that insects can be attracted to the bright light caused by concentrated solar technology, and as a result birds that hunt them can be ...

9

In the UK, the sun does not shine every day. We also need the most power in winter when the sun shines the least. Therefore every solar power station must be backed up by anther power station that can work when the sun is not shining. Concentrated solar power allows short term storage of the steam, so at least copes with 5 minutes of cloud cover, it ...

5

Basically, yes, but any shading caused by buildings / other obstructions may make one direction preferential. You can find sites that will do simulations online...

4

And so, as promised, I'll do it. First assumption: Let's work with 1m long strips of gutter. It'll be easier to calculate everything starting from here. Let's say the gutter is already full of ice. (We'll work on the ice filling problem later on) The standard gutter size (according to this site) is 5-inch K-Style, or 6-inch half round. If we use the half ...

4

Putting a single panel in series with two other panels that are in parallel does not accomplish what you think it does. The overall current of such a setup is limited by the single panel to 200 mA, so the three panels will not produce any more power than you'd get by just putting two panels in series. A single solar cell can be thought of as a current ...

3

Concentrated solar power plants are best located in isolated areas that receive a lot of sunshine all year round, which basically means arid or semi-arid regions. Most of these regions don't have large populations so long power transmission lines will be needed. To increase performance and efficiency, each CSP plant will need to be uniquely designed and ...

3

Torque is proportional to current. If you can't supply the full current, then the torque will be lower than it would be otherwise. The highest current draw is at startup when the motor is not turning. This means the motor will produce lower than intended torque when it tries to get going. If this torque isn't enough to get the motor moving, then it will ...

3

There are way too many details to get into here. However, do the basic first order analysis. Determine whether there is enough solar power over a day to keep the greenhouse at some temperature. You say you know all the dimensions and insulation values. Pick a plausible temperature differential between inside and outside, and compute the power required to ...

3

Earth axial tilt is 23.5°. For 11°N the solar altitude at noon of the equinoxes will be 90-11=79°; 90-11-23.5=55.5° at winter solstice and - it would be 90-11+23.5=102.5° at the summer solstice, but we normalize it to angle between nearest horizon and the Sun, so for values >90 we take 180-(value): 180-102.5=77.5° at the summer solstice. The actual solar ...

3

How complex this is depends on your needs. Once you know the solar flux, you need to calculate how much of that energy is absorbed by the wall (a function of the surface - how much is reflected? This itself may be a function of the angle of incidence, which will vary through the day...). This will heat up the outside of the wall, and it will start to conduct ...

2

That's a mess, and your labels about what is + and what is - out of each panel seem inconsistant. For the most effective use of the panels, wire them all in series. That will put out around 15 V under full sun. Now use a buck converter to make a regulated 5 V from that. There are many buck converter chips available off the shelf at these low voltages. ...

2

It sounds like what you are after is increased energy security. You want a backup which would have a very low load factor - it wouldn't get much use each year. You want fast response, times of high power, and a decent amount of storage. But it sounds like you don't need absolute continuity of power - it's ok if power goes out for a few seconds. Almost all ...

2

While black pipe in any configuration will collect heat from the sun, I recommend not reinventing the wheel. There are many companies around the world that manufacture low-cost black-vinyl solar collectors specifically for pool heating. If you do some price hunting you can likely get them cheaper than you could get the equivalent surface area of tubing. ...

2

You might want to take a look at commercial designs -- for example there are solar panels with fluid loops on the underside to extract waste heat exactly as you want to do. Now, on a technical note: ideally you'd like to maximize the heat transfer into your fluid. If you could cover the tubing (and/or the wall) with a material whose absorptance is high in ...

2

Crucial to this is how you intend to exploit this energy as this will be very significant in how quickly and uniformly heat is extracted from the target. 3000F is outside the working range of most readily available engineering materials and if you want something which can withstand that sort of temperature outright you are in the realms of things like ...

2

Plant load factor and capacity (use) factor are two names for the same thing: the ratio of mean power to rated nameplate capacity. Capacity factors between very similar or identical technologies that are serving a similar role on the grid, can be comparable: e.g coal and gas CCGT plants both working as baseload, or both working as mid-merit, or both working ...

2

It's the temperature coefficient of the panel. It varies by panel, but 0.005 (0.5%) is a fairly normal value for it. Its unit is 1/degree C. It's the rate at which cell efficiency drops off, as the cell temperature rises above 25 degrees C.

2

Solar heating systems have been designed with many different fluids depending on the ambient temperatures and max desired temperature. The ambient temperature is because the night-time temperature or even no sun temperature will affect the performance of the fluid. Some systems are designed to be above the boiling point of water so the system pressure is ...

1

Does your "reduce cost" objective include the cost of installing a duplicated house wiring system (including safety devices like breakers - not just stringing a few wires around!), and then ensuring that you never destroy an appliance by connecting it to the wrong supply? To do that reliably, you would need a different (and probably "non-standard") type of ...

1

Per the non-imaging optics wiki, C is the "ratio of input and output aperture areas". It is not efficiency like it is in some other equations. So putting a 45 degree half angle into the equation gives C = 2. This means that if the input area is 1m^2 then the output will be 0.5m^2. A solar radiation intensity would increase from say 1000w/m^2 to 2000w/m^2. ...

1

I found out the answer. The isolated subpanel serves a load-center or distribution panel for backup loads (incase of power outage, etc).

1

The answers to (a) and (b) depend on the peak load you want to use - i.e. the highest powered devices you want to run. Note that these might be things that you only run for a few minutes (e.g. an electric kettle), so they don't eat up the whole of your daily 4.4kWh energy budget. The answer to (c) is "no". For example, suppose your appliances used 1100W for ...

1

You can get the energy gained from heating by multiplying the heat capacity with the temperature difference and the amount of medium heated. Assuming you use water as a medium with a specific heat capacity of $4.2~J/(g~K)$ and mass density of $1000~g/l$ your typical situation as you described ($\Delta T =15~K$, flow = $15~l/min$) would come out to be  15~...

1

I'm not aware of any small scale historical versions, but it seems more-or-less possible. There is a good myth about the ancient Greek's using shields to focus sunlight and light Roman ships on fire. I see a few engineering challenges. You either have to have a nice roughly parabolic shaped mirror, which was really tough to manufacture until the last ...

1

Well, I think the French built a large one... See https://anglophone-direct.com/mont-louisfont-romeu-odeillo-via/ As for historical, the issue may have been the quality of the mirrors... And, 1000 years ago - understanding that the power was available as well as reliability ie not weather dependant.

1

Do not put a photosensor or sun-finder on your array. Your real-time clock may use the astronomy algorithms provided by Sandia National Lab to be very certain about where the sun is at any given time. (See link below) Please install a GPS, however, so that your time will be accurate as well as your exact location on the Earth's surface. Find out how much ...

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