solar panel

Kiaora_oap

hi
it's a bit off the wall idea I have. Since having an extension built on the back my house, the kitchen is not as light as i would like.
my plan is to install a sun light in the kitchen, but not as they are normally fitted, with a light tube, but with a round bright led lamp.
my plan is to fit a solar panel to run the lamp in the day time, to simulate daylight. so the lamp will come on and off as the days come and go.
I'm looking for some advice on panel size to run, say, 10/20w or even 30w led lamp ?
my ideal is the sun comes up, the light comes on, the sun goes down , the light goes off automatically , like a natural cycle.
thanks in advance for any input to my question
kiaora ! 

Petriix

It wouldn't be incredibly difficult to wire in a light sensor to switch it off when it gets dark. It probably wouldn't be cost effective to actually wire it to a solar panel.

Reed_Richards

The solar panel is your light sensor, @Petriix.

Mickey666

Have you already tried using a suitable LED lamp during day and found it to be adequate?  I ask because daylight is incredibly bright and lamps (even LED ones) are incredibly dim by comparison.  We don't really notice this day/night difference too much because our eyes (and brain) are very good at adapting to this range of light.   But when we can see both at the same time then the LED lamp might seem very dim indeed.   Just a thought, and worth some experimentation before splashing out on a solar panel.

If you decide that an LED lamp is a suitable boost to the existing daylight then you need to figure out how to use a solar panel for the use you've outlined.  The basic problem is that you won't be able to simply connect the solar panel to the LED lamp - this is because the voltage output of the panel will vary enormously, from zero volts (when it's dark) to perhaps 25+ volts when it's bright sunshine and few LED lamps will be happy with such a voltage swing.

One way to overcome this is to use a charge controller in conjunction with a battery.  The battery provides a constant, fixed voltage and the charge controller converts the varying solar panel voltage into constant voltage to keep the battery fully charged.  In this way the LED lamp is driven by a constant voltage,as it would normally expect.  You can get 12v LED lamps of varying wattage or you could add an inverter that would convert the battery voltage to mains voltage so you could then use standard domestic LED lamps if you wish.  This is the sort of system commonly used in caravan and camper vans and there are many retailers that specialise in such systems and would be able to advise what size solar panel and battery would be needed for your specific application.

However, even with such a system there's still the issue of ensuring the LED lamp only operates during the day to simulate daylight, but this could be easily achieved with a timer or, even better, a daylight sensor fitted outdoors somewhere to switch the light off during the hours of darkness.

Or, now that there is a battery in the system, why not size the system so that the system would be able to power the light during the day AND during the evening as well?    With the right sized components, the solar panel would be able to power the LED lamp and charge the battery during the day and the battery would be able to power the Lamp during the evening (I'm guessing you wouldn't need it past about midnight?).

Basically, all things are possible, though some things are simpler than others.  For instance, the sort of system described would certainly cost a few £100 whereas simply switching on a mains-powered 30W LED lamp would be far easier and even assuming it was on for 18 hours every day that would only be 540 Wh or a little over half a unit, so about 8p per day or about £30 per year, in which case it could easily take 10 years to achieve payback compared to a solar panel system.

Anyway, just a few thoughts.  

[Deleted User]

According to some sites a 30 watt LED bulb is equivalent to a 300 watt halogen. Surely this would give you a ‘beam me up Scotty’ pillar of light unless you can find a clever away of scattering the light around the room.

Kiaora_oap

hi
thank you for your very good reply. i see what you mean about the efficiency, (out lay to payback) and it's not very good in that way I'm planning. i did think of installing a light tube, but it's not practical in my situation. i suppose the out lay of the sun tube is not a good efficiency 
I have a led strip light around 1400mm long, 30w, in the back part of the kitchen, this is fine for the job in hand ,
the main reason for this project, for some reason i feel if the light was on all day, and powered by daylight/the sun. it would make me happier. almost like a natural life  cycle .
i imagine a round led lamp say 30w (the sun) lighting up at sunrise and off at sunset, or an led square 'window'
i think what you propose is a great idea, so materials, 1 x solar panel 1 x battery 1 x charge controller and 1 x light sensor.
ref the panel and battery, any idea of size of panel ?
and ref battery, would the type in emergency lights be good enough ? i don't want it to work at night 

thanks again for a great reply, and if you can point me in the direction for panel size and battery type it would be great

regards
kiaora 

Kiaora_oap

Dolor said:

According to some sites a 30 watt LED bulb is equivalent to a 300 watt halogen. Surely this would give you a ‘beam me up Scotty’ pillar of light unless you can find a clever away of scattering the light around the room.

hi
i did want to just run it off the panel, and let the sun decide when it put the light on or off.
the natural rhythm of life on earth ! 
but it appears i need some control on the panel, unless there is a way of controlling the power supply without a battery ?
maybe a circuit with a drain for anything over 12v
i have a 30w led strip light at the moment and its fine
thanks for your input
regards
kiaora

[Deleted User]

Kiaora_oap said:

Dolor said:

According to some sites a 30 watt LED bulb is equivalent to a 300 watt halogen. Surely this would give you a ‘beam me up Scotty’ pillar of light unless you can find a clever away of scattering the light around the room.

hi
i did want to just run it off the panel, and let the sun decide when it put the light on or off.
the natural rhythm of life on earth ! 
but it appears i need some control on the panel, unless there is a way of controlling the power supply without a battery ?
maybe a circuit with a drain for anything over 12v
i have a 30w led strip light at the moment and its fine
thanks for your input
regards
kiaora

In your original post, you said 'the kitchen is not as light as i would like'. Isn't there a slight flaw in your logic?

We need artificial light when natural light levels are low: when natural light levels are low, then solar panels are of little use unless you have a large array. For example, I have 7kWp of panels on my roof and my daily output this month has varied from 3.6kWhs to 33kWhs with instant power varying from 100 watts to 5kWs. Scale the solar panel size down and you might find that your 30watt LED bulb is as dim as a Toc H lamp when you need it the most.

Kiaora_oap

[Deleted User] said:

Kiaora_oap said:

[Deleted User] said:

According to some sites a 30 watt LED bulb is equivalent to a 300 watt halogen. Surely this would give you a ‘beam me up Scotty’ pillar of light unless you can find a clever away of scattering the light around the room.

hi
i did want to just run it off the panel, and let the sun decide when it put the light on or off.
the natural rhythm of life on earth ! 
but it appears i need some control on the panel, unless there is a way of controlling the power supply without a battery ?
maybe a circuit with a drain for anything over 12v
i have a 30w led strip light at the moment and its fine
thanks for your input
regards
kiaora

In your original post, you said 'the kitchen is not as light as i would like'. Isn't there a slight flaw in your logic?

We need artificial light when natural light levels are low: when natural light levels are low, then solar panels are of little use unless you have a large array. For example, I have 7kWp of panels on my roof and my daily output this month has varied from 3.6kWhs to 33kWhs with instant power varying from 100 watts to 5kWs. Scale the solar panel size down and you might find that your 30watt LED bulb is as dim as a Toc H lamp when you need it the most.

hi
I think I may be on a sharp leaning curve here.!
if I get this right, I may need 2-3kWp to run a 30w led lamp ?
If I install the panels myself, how would I use the excess power in the house ? if connected to the house wiring, would it drive the electric meter back ?
I've not heard the phrase about the Toc H lamp for a very long time ! nice one.

thanks again for your input
regards
kiaora

[Deleted User]

I suspect that you need to look at something similar to this type of arrangement. Bear in mind that batteries do go flat.

https://www.photonicuniverse.com/en/catalog/full/148-15W-Off-Grid-Solar-Lighting-System-with-4-LED-Lights-Solar-Panel-and-Battery.html?gclid=Cj0KCQjwwLKFBhDPARIsAPzPi-KsDR_R_6TgF2pgWar98tWVO7Eq1NsdBoj0p0e-kw-8fHuTDJIgTvYaArlOEALw_wcB

Kiaora_oap

hi
thanks for that, I'll look into it, 
regards
kiaora