{"action":"created","issue":{"url":"https://api.github.com/repos/pvlib/pvlib-python/issues/358","repository_url":"https://api.github.com/repos/pvlib/pvlib-python","labels_url":"https://api.github.com/repos/pvlib/pvlib-python/issues/358/labels{/name}","comments_url":"https://api.github.com/repos/pvlib/pvlib-python/issues/358/comments","events_url":"https://api.github.com/repos/pvlib/pvlib-python/issues/358/events","html_url":"https://github.com/pvlib/pvlib-python/issues/358","id":248125147,"number":358,"title":"Get a peak AC power around 6:00 am in the morning","user":{"login":"jielianguo","id":26880408,"avatar_url":"https://avatars2.githubusercontent.com/u/26880408?v=4","gravatar_id":"","url":"https://api.github.com/users/jielianguo","html_url":"https://github.com/jielianguo","followers_url":"https://api.github.com/users/jielianguo/followers","following_url":"https://api.github.com/users/jielianguo/following{/other_user}","gists_url":"https://api.github.com/users/jielianguo/gists{/gist_id}","starred_url":"https://api.github.com/users/jielianguo/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/jielianguo/subscriptions","organizations_url":"https://api.github.com/users/jielianguo/orgs","repos_url":"https://api.github.com/users/jielianguo/repos","events_url":"https://api.github.com/users/jielianguo/events{/privacy}","received_events_url":"https://api.github.com/users/jielianguo/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":7,"created_at":"2017-08-04T21:47:14Z","updated_at":"2017-08-08T15:17:44Z","closed_at":null,"body":"I run the bellowing code and got a high AC power at 6:00 am.\r\n  \r\n```python\r\nimport pandas as pd\r\nimport matplotlib.pyplot as plt\r\nimport datetime\r\nimport sys\r\n# seaborn makes the plots look nicer\r\nimport seaborn as sns; sns.set_color_codes()\r\nfrom pvlib.forecast import GFS, NAM, NDFD, HRRR, RAP,ForecastModel\r\nfrom pvlib.pvsystem import PVSystem, retrieve_sam\r\nfrom pvlib.tracking import SingleAxisTracker\r\nfrom pvlib.modelchain import ModelChain\r\nfrom pvlib.location import Location\r\n\r\nsandia_modules = retrieve_sam('sandiamod')\r\ncec_modules = retrieve_sam('CECMod')\r\ncec_inverters = retrieve_sam('cecinverter')\r\nmodule = sandia_modules['Trina_TSM_240PA05__2013_']\r\ninverter = cec_inverters['SolarEdge_Technologies__SE9K_208V__CEC_2013_']\r\nprint(module)\r\n\r\nlatitude, longitude, tz = 53.622537, -113.644237, 'Canada/Mountain'\r\nstart = pd.Timestamp('07/30/2017 00:00:00', tz=tz)\r\nend = start + pd.Timedelta(days=5)\r\nfx_model = RAP(set_type ='best') \r\nfx_data = fx_model.get_processed_data(latitude, longitude, start, end)\r\n\r\nsystem = PVSystem(module_parameters=module,\\\r\n                  inverter_parameters=inverter,\\\r\n                  modules_per_string=22,\\\r\n                  strings_per_inverter=2,surface_tilt = 10,surface_azimuth =150 )\r\nmc = ModelChain(system, fx_model.location,name= 'pv')\r\nmc.run_model(fx_data.index, weather=fx_data)\r\n\r\nmc.ac.plot()\r\nplt.ylim(0, None)\r\nplt.ylabel('AC Power (W)')\r\n```\r\n![image](https://user-images.githubusercontent.com/26880408/28986996-01d33122-792f-11e7-92a7-35b4ddf8ae38.png)\r\n\r\n\r\nThe spectral_modifier (spectral loss) in the bellowing code is high at 6:00 am. Multiplying spectral_modifier to get effective irradiance makes the effective irradiance high at 6:00 am, which ultimately leads to a high AC power. I am not sure if the formula to get the effective_irradiance is correct.   \r\n```python\r\n    def effective_irradiance_model(self):\r\n        fd = self.system.module_parameters.get('FD', 1.)\r\n        self.effective_irradiance = self.spectral_modifier * (\r\n            self.total_irrad['poa_direct']*self.aoi_modifier +\r\n            fd*self.total_irrad['poa_diffuse'])\r\n        print('aoi_modifier')\r\n        print(self.aoi_modifier)\r\n\r\n        return self\r\n```"},"comment":{"url":"https://api.github.com/repos/pvlib/pvlib-python/issues/comments/320988598","html_url":"https://github.com/pvlib/pvlib-python/issues/358#issuecomment-320988598","issue_url":"https://api.github.com/repos/pvlib/pvlib-python/issues/358","id":320988598,"user":{"login":"cwhanse","id":5393711,"avatar_url":"https://avatars1.githubusercontent.com/u/5393711?v=4","gravatar_id":"","url":"https://api.github.com/users/cwhanse","html_url":"https://github.com/cwhanse","followers_url":"https://api.github.com/users/cwhanse/followers","following_url":"https://api.github.com/users/cwhanse/following{/other_user}","gists_url":"https://api.github.com/users/cwhanse/gists{/gist_id}","starred_url":"https://api.github.com/users/cwhanse/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/cwhanse/subscriptions","organizations_url":"https://api.github.com/users/cwhanse/orgs","repos_url":"https://api.github.com/users/cwhanse/repos","events_url":"https://api.github.com/users/cwhanse/events{/privacy}","received_events_url":"https://api.github.com/users/cwhanse/received_events","type":"User","site_admin":false},"created_at":"2017-08-08T15:17:44Z","updated_at":"2017-08-08T15:17:44Z","body":"@adriesse I agree, a polynomial is a poor choice, but it was made years ago and is now baked into the parameter databases. We ought to replace it with a functional form which has constrained asymptotic behavior, but that's a discussion not for pvlib GitHub."}}
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