Geekzone: technology news, blogs, forums
Guest
Welcome Guest.
You haven't logged in yet. If you don't have an account you can register now.




545 posts

Ultimate Geek
+1 received by user: 173


Topic # 222771 28-Aug-2017 10:25
Send private message quote this post

Until the government forces utilities to pay a reasonable amount to buy back electricity looks like solar electric is not good for return on investment. This website showed at least 20 years ROI for my home.

https://www.energywise.govt.nz/tools/solar-calculator/

So on to the subject at hand. I have a split level house, with the living area upstairs.

I was thinking of using an inexpensive solar box to provide some heating.

2 x 4 meters, facing south. At 90% efficiency, it's supposed to produce around 400 watts per square meter or 3,200 watts of heating when it's sunny. My guess on DIY price would be around $1,000.

So far I've come up with these plans, which seem the easiest / cheapest

Click to see full size
http://www.builditsolar.com/Experimental/DeepMeshCol/120116Test.htm

Anyone tried something similar?

Calculating optimal angle in New Zealand
http://www.solardirect.co.nz/Solar_panel_collector_angle.html





Create new topic
1972 posts

Uber Geek
+1 received by user: 629

Subscriber

  Reply # 1854460 28-Aug-2017 23:28
2 people support this post
Send private message quote this post

How much output do you get when it is overcast? I have solar hot water on my house - selective surface vacuum tube type. 50 tubes on a 300L HWC. In the morning, cylinder upper and lower temp sensors were bot at 16deg. And when I got home - 45deg. Not bad considering the weather wasn't the best today. Even when it it is overcast with light drizzle - they still produce a little bit of hot water. And with enough sun, they will happily get the cylinder up to boiling. I had to install a heat dump system. (sends excess heat to the spa pool). As the temp relief valve kept on dumping the whole cylinder worth of near boiling water during summer. (cylinder temp now limited to max 80deg).

 

On continuously overcast days, the system typically heats the cylinder from 15deg to 25deg or so. It doesn't sound like much, but that is still a 1/4 to 1/3rd saving on the amount of electrical heating needed.

 

And solar PV panels on a MPPT charger, will supposedly still provide 10-15% of their rated output even on overcast days.

 

I just don't think building such a system would be worth it unless you figure out where to buy those special selective surface coatings. (absorbs solar radiation well, but poor at radiating heat) Even when my solar panels are running at high temps, the tubes feel cold to touch.

 

As for solar buyback rates - longterm wholesale electricity prices are around 7.5c per KW/Hr. So why should your power company pay you more for solar power, compared to power generated by other renewable generation sources? And even today people with gridtie solar get an indirect subsidy via the low use charges, As they pay less lines fees in total, yet their peak demand is still exactly the same. Despite having solar.






20374 posts

Uber Geek
+1 received by user: 3878

Trusted
Subscriber

  Reply # 1854463 28-Aug-2017 23:31
Send private message quote this post

Aredwood:

 

As for solar buyback rates - longterm wholesale electricity prices are around 7.5c per KW/Hr. So why should your power company pay you more for solar power, compared to power generated by other renewable generation sources? And even today people with gridtie solar get an indirect subsidy via the low use charges, As they pay less lines fees in total, yet their peak demand is still exactly the same. Despite having solar.

 

 

Low use charges? What? I pay the exact same rates as before solar went in, only difference is the few c credits I get for the inadvertant export which is usually because something tripped off thanks to the *(&(*&)(^(&* RCDs that I have to have now. Yay for driving home because of a cold aquarium alert.





Richard rich.ms

 
 
 
 


1972 posts

Uber Geek
+1 received by user: 629

Subscriber

  Reply # 1854486 29-Aug-2017 01:08
Send private message quote this post

It doesn't apply much to you @richms as you still use enough power to still be on standard user rates despite having solar. (from what I remember you have said in other threads). But often people who have gridtie solar, will be on the low user plan. And since the low user plan has artificially cheap fixed fees combined with an artificially high unit cost. Having solar on a low user plan means that you get a bigger saving than what you otherwise would.

 

These low user subsidies also mean that power companies must make the standard user plans slightly more expensive. As they are not allowed to offer any pricing plans that will give a lower overall bill than the low user plans. For someone who uses less than 8000 units per year. And since gridtie solar doesn't reduce peak demand, you end up with lots more people on low user rates, as they have low power usage averaged over the whole year. Yet they still have really high peak demand on cold winter's evenings.

 

 

 

As for the Aquarium heaters, try running them through an isolating transformer. Im guessing that there is a little bit of earth leakage through the elements that is tripping the RCDs.

 

Im dreading the inevitable switchboard upgrade that I will need when I get the new underground mains cable installed on my house. Again because of RCDs, which will always trip on me as I have some really long cable runs downstream of my switchboard. And even worse it is on the diagonally opposite corner of my house from the kitchen.






Create new topic



Twitter »

Follow us to receive Twitter updates when new discussions are posted in our forums:



Follow us to receive Twitter updates when news items and blogs are posted in our frontpage:



Follow us to receive Twitter updates when tech item prices are listed in our price comparison site:





News »

Symantec selects Amazon Web Services to deliver cloud security
Posted 23-Nov-2017 10:40


New Zealand Ministry of Education chooses Unisys for cloud-based education resourcing management system
Posted 22-Nov-2017 22:00


Business analytics software powers profits for NZ wine producers
Posted 22-Nov-2017 21:52


Pyrios strikes up alliance with Microsoft integrator UC Logiq
Posted 22-Nov-2017 21:51


The New Zealand IT services ecosystem - it's all digital down here
Posted 22-Nov-2017 21:49


Volvo to supply tens of thousands of autonomous drive compatible cars to Uber
Posted 22-Nov-2017 21:46


From small to medium and beyond: Navigating the ERP battlefield
Posted 21-Nov-2017 21:12


Business owners: ERP software selection starts (and finishes) with you
Posted 21-Nov-2017 21:11


Why I'm not an early adopter
Posted 21-Nov-2017 10:39


Netatmo launches smart home products in New Zealand
Posted 20-Nov-2017 20:06


Huawei Mate 10: Punchy, long battery life, artificial intelligence
Posted 20-Nov-2017 16:30


Propel launch Disney Star Wars Laser Battle Drones
Posted 19-Nov-2017 21:26


UFB killer app: Speed
Posted 17-Nov-2017 17:01


The case for RSS — MacSparky
Posted 13-Nov-2017 14:35


WordPress and Indieweb: Take control of your online presence — 6:30 GridAKL Nov 30
Posted 11-Nov-2017 13:43



Geekzone Live »

Try automatic live updates from Geekzone directly in your browser, without refreshing the page, with Geekzone Live now.



Are you subscribed to our RSS feed? You can download the latest headlines and summaries from our stories directly to your computer or smartphone by using a feed reader.

Alternatively, you can receive a daily email with Geekzone updates.