So­lar nuts and bolts

Made up your mind to get so­lar pan­els on your roof? Here’s what you need to know.

Element - - Contents - By Rosie Bos­worth

Since we aren’t all so­lar gu­rus, we’ve taken it on our­selves to do the nitty gritty re­search for you and put the shine into so­lar so you have the ba­sic need-to-knows if you’re think­ing about in­stalling so­lar at home, the of­fice or your sun-drenched sum­mer bach.

No longer just a nice-to-have lux­ury for the fi­nan­cially elite, so­lar tech­nol­ogy and eco­nomic payback have im­proved dra­mat­i­cally in re­cent years and in­stalling so­lar onto your home or business is be­com­ing in­creas­ingly straight­for­ward – if you know the ba­sics.

The stan­dard so­lar pho­to­voltaic (PV) res­i­den­tial in­stal­la­tion con­sists of not only pan­els, also of­ten re­ferred to as “mod­ules”, but also an in­verter – the power con­troller, or “brains” of the sys­tem, and the as­so­ci­ated rack­ing and mount­ing sys­tem. Most are grid-con­nected (wired into the Na­tional Grid), but some have bat­tery stor­age, and some have both.

So­lar pan­els Pan­els are es­sen­tially the solid-state, pas­sive com­po­nent of the so­lar power sys­tem. A wide range of so­lar pan­els are avail­able in­ter­na­tion­ally, and a plethora of brands are now on the New Zealand mar­ket. But not all so­lar pan­els are cre­ated equal and a key con­sid­er­a­tion to take on board when in­vest­ing in so­lar is, first and fore­most, the qual­ity of the com­po­nents used.

As a way to help you dis­tin­guish the wheat from the chaff the in­dus­try has de­vel­oped a three-tier rat­ing sys­tem (Tier 1, 2 or 3) that ranks the nu­mer­ous panel man­u­fac­tur­ers in terms of their qual­ity, re­li­a­bil­ity and his­tory.

Tier 1 rep­re­sents only a small slice of the to­tal num­ber of man­u­fac­tur­ers on the mar­ket (2%) but is by far the best op­tion to choose. A num­ber of at­tributes clearly sets them apart from their com­peti­tors. First, man­u­fac­tur­ers are ‘ver­ti­cally in­te­grated’, mean­ing the company you’re in­vest­ing in con­trols the en­tire pro­duc­tion process and is ac­count­able for ev­ery­thing – from the sil­i­con cells to the mod­ules, frames and ul­ti­mately panel assem­bly. Tier 1 man­u­fac­tur­ers have also in­vested heav­ily in re­search and de­vel­op­ment (R&D), use highly au­to­mated man­u­fac­tur­ing tech­niques and have at least five years’ his­tory in man­u­fac­tur­ing so­lar pan­els. In other words, if some­thing goes wrong you know you’re safely cov­ered and there’s a high like­li­hood that that company will still be afloat in 20 years’ time to hon­our its war­ranties.

Tier 2 man­u­fac­tur­ers ranked are the mid­dle ground, and com­prise 8% of the mar­ket. They have less ex­pe­ri­ence in pro­duc­ing pan­els (2 – 5 years) and invest rel­a­tively lit­tle in R&D com­pared to Tier 1. Com­pris­ing the bulk of the mar­ket (90%), Tier 3 man­u­fac­tur­ers typ­i­cally as­sem­ble pan­els us­ing com­po­nents man­u­fac­tured by other com­pa­nies. They also have the least ex­pe­ri­ence, in­vest­ment fo­cus and cred­i­bil­ity.

To en­sure you don’t end up with a le­mon of a so­lar sys­tem, it is im­por­tant to make sure that the pan­els that you pur­chase are from rep­utable Tier 1 man­u­fac­tur­ers. For­tu­nately most pan­els avail­able in NZ are Tier 1 or, at worst, Tier 2 prod­ucts. In­ter­na­tion­ally, there are cases of house fires be­ing caused by faulty pan­els. Fur­ther, while Tier 1 op­tions ap­pear more costly than Tiers 2 and 3, the war­ranty on the prod­uct is only as good as the company be­hind it. Some prod­ucts on the mar­ket boast long or ex­tended war­ranty terms, but when you look closer the war­ranty is “un­der­writ­ten” by a third party. Th­ese war­ranties are hence only good while the pre­mium is be­ing paid. In the event the company where pan­els are sourced cease business for any rea­son or stop pay­ing the war­ranty you will likely have prob­lems claim­ing in the case of prod­uct fail­ure.

The brains

If pan­els are the hard­ware to your so­lar sys­tem, the ‘in­verter” is the brains be­hind it. The most elec­tron­i­cally com­plex part of the sys­tem, the in­verter es­sen­tially coverts the di­rect cur­rent (DC) gen­er­ated by the so­lar pan­els into al­ter­nat­ing cur­rent (AC) – the power that can be used in your home. The in­verter also has in­built pro­tec­tion cir­cuits to con­trol the im­port and ex­port of gen­er­ated power from the sys­tem.

Make sure you pri­ori­tise high qual­ity over cost when buy­ing an in­verter. This is be­cause more of­ten than not so­lar sys­tem fail­ures are due to in­verter fail­ure rather than panel fail­ure. This is also im­por­tant be­cause the tier sys­tem doesn’t ap­ply for in­vert­ers, so you have to do your home­work on the qual­ity of the prod­uct.

Mi­cro in­vert­ers

Mi­cro In­vert­ers are be­com­ing more common. With a small in­verter at­tached to each so­lar panel, they covert power from DC to AC at the panel – rather than at one sin­gle point in the sys­tem. The ben­e­fits are that if one panel is shaded then only the so­lar pro­duc­tion of that panel is af­fected. With con­ven­tional, less costly, “string” in­vert­ers, if one panel is shaded then the whole ar­ray’s per­for­mance is limited to the level of the low­est pro­duc­ing panel.

Nonethe­less, un­less you en­vis­age hav­ing sig­nif­i­cant shad­ing is­sues the price pre­mium of mi­cro in­vert­ers is gen­er­ally un­nec­es­sary. If your prop­erty is some­where in the mid­dle – where par­tial shad­ing is likely, then ‘op­ti­mised pan­els’ can of­fer an al­ter­na­tive so­lu­tion. Th­ese have in­built op­ti­mis­ers into each panel that in­di­vid­u­ally op­ti­mise each panel’s out­put and per­for­mance like mi­cro in­vert­ers, but with­out chang­ing the cur­rent at panel level.

So­lar stor­age

So­lar stor­age (bat­tery) tech­nol­ogy has not kept pace with so­lar cell tech­nol­ogy, and nei­ther has the price drop. But as so­lar up­take and power prices con­tinue to soar the de­vel­op­ment of cost-ef­fec­tive, longlife bat­tery tech­nolo­gies is the en­ergy mar­ket’s fastest grow­ing sec­tor. It is now only a mat­ter of time be­fore af­ford­able ‘hy­brid’ so­lar sys­tems – ie those that have a level of bat­tery stor­age while also be­ing grid con­nected – be­comes a re­al­ity.

In­stal­la­tion

With your So­lar 101 lingo down­pat, un­der­stand­ing the process of con­nect­ing you up to so­lar– both at your home, and with a power company – is the next im­por­tant step. This process is rea­son­ably com­plex and oner­ous if you do it your­self, so choose an in­staller who can pro­vide an end-to-end so­lu­tion.

You first need per­mis­sion to con­nect to your lo­cal power net­work prior to in­stal­la­tion (in­volv­ing ap­pli­ca­tion doc­u­men­ta­tion and sub­mit­ting sys­tem de­sign de­tails and elec­tri­cal spec­i­fi­ca­tion). Then you need to have a regis­tered elec­tri­cian in­stall it. After this it must be in­spected and is­sued a cer­tifi­cate of com­pli­ance by a regis­tered elec­tri­cal in­spec­tor. An ap­pli­ca­tion must also be made to your power re­tailer to swap your ex­ist­ing me­ter out with one that will mea­sure both im­ported (power from the power company) and ex­ported (so­lar) power. This new me­ter can take up to two months to in­stall and only after this is done are you able to en­joy the cash ben­e­fits of your new sys­tem.

It’s up to you to de­cide on your elec­tric­ity provider. Cur­rently Merid­ian and Mer­cury En­ergy are the best, of­fer­ing de­cent rates for the ex­cess power you pro­duce.

On­go­ing main­te­nance and mon­i­tor­ing

Gen­er­ally speak­ing, reg­u­larly clean­ing the pan­els and an an­nual sup­plier check of the sys­tem to en­sure that the sys­tem is op­er­at­ing prop­erly are suf­fi­cient. From a per­for­mance mon­i­tor­ing per­spec­tive, whether you’re in­ter­ested in daily per­for­mance or in the monthly power sav­ings, most in­vert­ers in­clude sim­ple read­outs to wire­less or Blue­tooth mon­i­tor­ing via lap­top or smart­phone to in­di­cate your sys­tem’s per­for­mance. The level of mon­i­tor­ing is up to you. Ad­vanced sys­tems on the mar­ket mon­i­tor both so­lar and mains power us­age, are es­pe­cially use­ful in com­mer­cial ap­pli­ca­tions where the sys­tem can mea­sure us­age by var­i­ous as­pects of a prop­erty’s en­ergy con­sump­tion such as lights, air­con or elec­tronic equip­ment.

War­ran­tees

In terms of war­ranty cover there are two things you need to look out for. The first is the man­u­fac­turer’s prod­uct war­ranty of the pan­els. This cov­ers against panel man­u­fac­tur­ing faults and pro­vides a 10 – 12 year prod­uct warrantee. The sec­ond con­cerns power pro­duc­tion and gen­er­ally war­rants power pro­duc­tion on a slid­ing scale over 25 years. Bet­ter pan­els gen­er­ally war­rant a pro­duc­tion of 90% or bet­ter after 10 years and 80% or more after 25 years. It is also use­ful to look for es­tab­lished, rep­utable sup­pli­ers who of­fer on­go­ing main­te­nance pro­grammes.

Long-term con­sid­er­a­tions

If you are think­ing about adding bat­tery stor­age to your so­lar sys­tem in the fu­ture, con­sid­erthe cost and con­ve­nience of do­ing so, and ques­tion whether mi­cro in­vert­ers are in fact the best so­lu­tion to choose. Why? Stor­ing so­lar in bat­tery re­quires en­ergy to be re-in­verted back to DC to feed bat­ter­ies which adds un­nec­es­sary ex­pense and mul­ti­ple in­ver­sion de­creases over­all so­lar ef­fi­ciency.

In ad­di­tion to mak­ing sure you are pur­chas­ing a Tier 1 sys­tem, ver­ify that the in­stal­la­tion is be­ing com­pleted to reg­u­la­tion stan­dard. Make sure you are deal­ing with regis­tered master elec­tri­cians. It is also im­por­tant to make sure you are buy­ing the right size sys­tem for your re­quire­ments–last month’s El­e­ment ar­ti­cle on sys­tem siz­ing can help guide you on this (find it at el­e­ment­magazine. co.nz). Fi­nally, be wary of new­com­ers to the in­dus­try who may be here to­day and gone to­mor­row, leav­ing you with no on­go­ing support. This ed­i­to­rial se­ries is made pos­si­ble with fund­ing from So­lar King. To find out more about So­lar King’s prod­ucts visit so­lark­ing.co.nz

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