{"id":2924,"date":"2013-09-11T11:19:16","date_gmt":"2013-09-11T10:19:16","guid":{"rendered":"http:\/\/www.theoillamp.co.uk\/?p=2924"},"modified":"2014-03-28T12:40:39","modified_gmt":"2014-03-28T11:40:39","slug":"how-to-manage-excess-power","status":"publish","type":"post","link":"https:\/\/www.theoillamp.co.uk\/?p=2924","title":{"rendered":"How to manage excess power"},"content":{"rendered":"<p>In a <a href=\"https:\/\/www.theoillamp.co.uk\/?p=2893\" target=\"_blank\">previous post<\/a> on smart meters I raised the issue in passing of what to do with excess power output that may occur from very large penetration of\u00a0 PV systems on the low voltage grid.\u00a0 <a href=\"http:\/\/www.icis.com\/heren\/articles\/2011\/12\/12\/9515924\/germany-faces-struggle-to-balance-electricity-system-as-loop-flows.html\" target=\"_blank\">Germany<\/a> is <a href=\"http:\/\/www.engineeringnews.co.za\/print-version\/germany-also-struggling-to-get-energy-mix-balance-right-2011-01-21\" target=\"_blank\">facing<\/a> this issue now with wind and solar.\u00a0 During the working week in summer this is not an issue as German industry (which moans about the cost of electricity) absorbs all the sun power produced. The problem arises at weekends when the 32GWp of installed capacity (at the end of 2012) is operating at anything like full capacity.\u00a0 Last summer an estimate is that nearly 30GW of electricity was produced from the PV systems making up perhaps 50% of demand.\u00a0 Surprising although it may seem this is could be a serious issue.\u00a0 The problem is that if there is excess power on an electricity grid the voltage and grid frequency rise outside defined limits and the grid will shut down. So far the Germans seem to have managed the situation with few outages.\u00a0 There are a number of solutions briefly covered below to this.\u00a0 These are;<\/p>\n<ul>\n<li>Use the excess power yourself.\u00a0 Not an easy one this if lots of people are off work although as covered in the post linked to on this blog above smart grids and meters could help here by encouraging people to use washing machines and bread makers when electricity is cheap, which it will be when you have loads of it.<\/li>\n<\/ul>\n<ul>\n<li>Switch off conventional power stations.\u00a0 Obviously a whole heap of nuclear, coal and gas power stations are operating continuously providing baseload power.\u00a0 These can be taken off line (not nuclear since they takes weeks to start back up again).\u00a0 In fact recently RWE announced the permanent closure of a number of coal fired power stations as the wholesale power price had dropped too low to make them economically <a href=\"http:\/\/cleantechnica.com\/2013\/08\/18\/3-1-gw-of-fossil-fuel-power-plants-to-be-shut-down-in-germany-no-longer-competitive\/\" target=\"_blank\">viable<\/a>.\u00a0 Of course if you go too far down this line you will have insufficient electricity and a grid outage for that reason.\u00a0 Nevertheless its encouraging renewables are shutting coal down.<\/li>\n<\/ul>\n<ul>\n<li>Sell your excess power to your neighbours.\u00a0 Germany is doing this, despite the nuclear phaseout and the immediate shutting of a number of old reactors Germany is exporting large amounts of electricity and is a net <a href=\"http:\/\/www.infobarrel.com\/Has_Germany_Become_a_Cheap_Electricity_Supplier\" target=\"_blank\">exporter<\/a> of <a href=\"http:\/\/www.germany.info\/Vertretung\/usa\/en\/__pr\/P__Wash\/2013\/04\/04-Electricity-Exporter.html\" target=\"_blank\">electricity<\/a>. However, there are problems with this solution.\u00a0 First you may find they don&#8217;t need it.\u00a0 Second, the Germans are selling expensively subsidised electricity at a loss to their neighbours.\u00a0 It should be pointed out that these subsidies for new systems are much lower than they were and phase complete phase out of the FIT at 55GWp of installed capacity (which is only 2-3 years away) is planned.<\/li>\n<\/ul>\n<ul>\n<li>Store the excess power.\u00a0 Germany is building more pumped storage, but obviously this can only be a partial solution.<\/li>\n<\/ul>\n<ul>\n<li>With PV systems being the problem, could they be the solution?\u00a0 A number of solutions present themselves at the micro-generation scale.\u00a0 Firstly, the individual householder could be encouraged to store electricity and use it at night.\u00a0 The Germans are being encouraged to do this with a subsidy of some type, although uptake has been low.\u00a0 Second, the PV inverters which convert DC from the PV to AC for home or grid use monitor the grid conditions.\u00a0 In fact this is part of the problem.\u00a0 Say its a dull day in July and the sun comes out and PV is suddenly producing 50% of the electrical supply.\u00a0 The voltage rises and takes its outside the voltage limits set by the German government for PV inverters.\u00a0 Millions of inverters shut down but not before you have taken base coal fired power baseload generation off line.\u00a0 You go from feast to famine in minutes and have an outage.\u00a0 However, you can by regulation use this grid monitoring facility to aid this control of the grid in a number of different ways.\u00a0 You can set the inverter to trim its power output (lower its efficiency) when the grid conditions reach a certain voltage or frequency and switch off at a higher frequency (50.2Hz).\u00a0 This is what the Germans have <a href=\"http:\/\/www.ecofys.com\/files\/files\/ecofys_ifk_2011_50_2_hz_summary.pdf\" target=\"_blank\">done<\/a>.\u00a0 Another thing they are doing I understand is trying to encourage PV system installation on west facing roofs to spread the peak output over the day.\u00a0 Another strategy I would suggest is that inverters have different cut-off settings.\u00a0 So for example in the north of Germany the voltage and frequency settings are set higher than say in Bavaria where its sunnier.\u00a0 This means not all inverters cut power or cut at the same point and people in Northern Germany are not losing as much money.<\/li>\n<\/ul>\n<p>There is no doubt that excessive renewables production is a challenge, but one that is not unmanageable with probably all the strategies above required in combination.\u00a0 Since conventional fuels are finite we will have to cope with this problem at some point in the future. Other countries need to think about this.\u00a0 There is an estimate that in July the UK got 2.5% of its electricity from PV over 24 hours and about 6% at around midday.\u00a0 We are way behind Germany but we don&#8217;t need as much PV installed for us to catch up.<\/p>\n<p>Neil<\/p>\n","protected":false},"excerpt":{"rendered":"<p>In a previous post on smart meters I raised the issue in passing of what to do with excess power output that may occur from very large penetration of\u00a0 PV systems on the low voltage grid.\u00a0 Germany is facing this &hellip; <a href=\"https:\/\/www.theoillamp.co.uk\/?p=2924\">Continue reading <span class=\"meta-nav\">&rarr;<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"footnotes":""},"categories":[28,4],"tags":[],"class_list":["post-2924","post","type-post","status-publish","format-standard","hentry","category-other","category-renewables"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v25.8 - 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