Showing posts with label solar. Show all posts

Sunday, January 19, 2014

Solar in Seattle – One Year of Data

One Year of Solar Production Data for a Residential House in Seattle (Green = consumption, Yellow = production, Orange = net)

The graph attached to this post describes one year (2013) of data with our solar panels (in the "center of the universe" Fremont). At the beginning of 2013, we brought 14 panels on line, on the roof of our house. Each panel is a SolarWorld Sunmodule SW 255 W Mono Panel (rated for 255 Watts). Now, at the beginning of 2014, we are looking back and are surprised at the following:

78% of our electricity for 2013 came from our solar panels. It is the ratio between the yellow and green line in the graph. Or, totally, we generated 4074 kWh over the year and consumed 5,253 kWh.
On average, we consume 14.4 kWh/day and generate 11.1 kWh/day.
Our gross usage kWh/day decreased during the year. We think this is because of our increased awareness of energy usage. This is the green line in the graph.
You really notice when you have guests! Note the points on the graph on 10/1/13 when we had guests and our energy usage spiked.

The graph has three colors:

Green: our gross KWh/day consumption.
Yellow: our KWh/day solar production.
Orange: the net between consumption and production.

Interpretation of the graph:

The points on the graph are data measurements. They are not equally spaced, i.e., there is a variable amount of days between points.
When an orange data point (net) goes below zero, it means we were generating more than we were consuming.
A colored line reflects the average of the values up to given date.

In the post, Working with Your Solar Array data Using the Enphase API, we describe how we programmatically work with our solar data.

Here’s to a sunny 2014!

System details from Enphase Web Site. Selected Day, June 12 2013, was maximum production day.

Sunday, January 20, 2013

Note On Using the Enphase Power Today Method

Update: June 2015: In the move from v1 to v2 of the API, the power_today method was removed. See the migration guide. Use the stats method instead as show in Working with Your Solar Array Data Using the Enphase API. This information in this post will be kept for archival.

In a previous post Working with Your Solar Array Data Using the Enphase API we talked about using Enphase API data to retrieve data about a solar array and use the data for presentation in a web page. One of the problems (not apparent on first glance) is that the data didn’t have a timestamp. Instead, we were assigning a timestamp equal to the time we made the request. Our assigned timestamp does not equal the time the data was last updated.

Problem

We use the summary() method to return the energy_today value (Wh), but there is no useful timestamp that indicates as of what time the data is valid. The power_today() method returns values for the full day. Can we get a timestamp from this data? How is this data related to the summary() request?

Solution

We can use the power_today() method to return a timestamp. Furthermore, the data returned from the power_today() method “seems” to be track to the energy_today, but delayed.

Details

Step 1. Get the output of both the summary() and power_today() methods at the same time. In the example outputs below, it is 14:00 (military time). We’ll call this time the request_time.

{"energy_week":34865,"energy_month":94405,"modules":14,"current_power":477,"summary_date":"2013-01-20T00:00:00-08:00","source":"microinverters",
"energy_lifetime":95939,"system_id":XXXXXX,"energy_today":5121}
{"first_interval_end_date":"2013-01-20T00:05:00-08:00","production":[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,5,10,13,17,27,41,51,60,70,77,85,101,116,129,145,156,170,194,225,260,289,330,355,348,336,310,301,344,397,409,393,379,388,401,396,386,364,351,379,419,475,518,512,611,936,1597,2038,1988,2238,2322,2180,2033,2033,2011,1684,1424,1646,1811,1944,2104,2125,2171,2258,2239,2100,1916,1610,1236,1013,924],"interval_length":300}

Step 2. In the power_today() data, we see see that the interval_length is 300 (5 minutes) and first_interval_end_date was at 5 minutes after midnight. So the number of data points indicate the last time the data was updated. In this case, 5 min * 164 points / 60 min = 13.67 or in hh:mm 13:40. We’ll call this the calculated timestamp.

Note, if first_interval_end_date were not equal to interval_length, the timestamp calculation would be a bit more complicated. The more general calculation requires this fact to be taken into account and looks like this:

(Count(data points) * interval_length) ) / 60 min + (first_interval_end_date - midnight ) / 60 min = hours offset

But for the time of reporting we are doing here we can stick with the simpler formula:
(Count(data points) * interval_length) ) / 60 min

Step 3. In the power_today() data, we now sum the data points and get 58924. (Import as CSV into Excel.) The summed value is Watts, to get Watt hours we would take the interval for each data point multiplied by the value of the Watts, sum, and divide by 60 min which gives 4910 Wh. We’ll call this the calculated energy_today.

Step 4. In the summary() data, note that the energy_today value is 5121 Wh which is greater than the value for step 3. We’ll call this summary energy_today.

Step 5. Repeat data collection for a little while to see that the calculated energy_today is about 5-10 minutes behind in this small example. It might be more in different circumstances. Also, who knows what processing might be going on with the summary energy_today value.

request_time	calculated timestamp	calculated energy_today	summary energy_today
14:00	13:40	4910	5121
14:10	13:55	5142	5257
14:15	14:00	5205	5364
14:20	14:05	5282	5447
14:25	14:10	5377	5557
14:30	15:25	5481	5557*
14:35	15:20	5702	5869

* We just happened to catch a glitch where the value did not update, which can happen.
So on first glance it looks like we can use the power_today() values to help establish a timestamp. You might be thinking, if we are lazy, on average we could say that the summary energy_today has a timestamp of request_time minus 5-10 minutes. That would apply in an ideal world of consistent data updates. But what if the web service stopped reporting new data points because? In that case, we would want to know this and the calculated timestamp would indicate it. So, if you are after a more precise timestamp use the calculated timestamp.

Sunday, January 13, 2013

Working with Your Solar Array Data Using the Enphase API

Overview

(This post last reviewed and steps verified October 2015. Note that WebMatrix has been retired since this was written.)

Left: Example Web Service Call Data; Right: Enphase Graphic Showing Solar Panel Array

Enphase Graphic Showing Solar Panel Array

This tutorial discusses a simple approach to working with your Enphase data. Enphase data is data that your solar array sends up into the cloud (Enphase servers) when your system uses the Enphase Envoy Communications Gateway (http://enphase.com/products/envoy/) with your Enphase microinverters. This system allows solar array owners to check the status of their system and view various aspects of the system's performance.

We recently installed 14 solar panels working with Solterra Systems and we were curious about how to access our data. It proved to be fairly straightforward. With a little programming background you can work with the data as you want, for example, exposing it in web pages and applications.
Don’t know or want to do any programming? No worries, you you can still work with your Enphase data in several easy ways:

Probably the easiest non-programming approach is to just go to the site that Enphase provides for you. (Sites can be made public or remain private.) Enphase provides all sorts of graphs. For example: https://enlighten.enphaseenergy.com/public/systems/zVU7148952
The next easiest non-programming approach is to log on, locally, to your Enphase Envoy gateway device and view your data. This only works when you are at home, on your own network.

The local site might be something like http://192.168.0.11 and it includes a couple of pages:

Home page - System statistics and events.
Production page - System energy production
Inventory page - list of solar array panels (at least for us).
Administration page

It seems strange to have data about something physically near us pump its data out to the Internet where we then access back through the Internet. Why do we do this? Because the local data isn't easily consumable in any practical form other than viewing it in a browser. What we want are numbers we can manipulate and display as we want.
A third non-programming approach is to get an API key as shown in Step 1 below and within a few moments you can create a URL that you can use in a browser to return data. It is pretty low tech, but it works wherever you are. Here’s an example of an URL: https://api.enphaseenergy.com/api/systems?key=<YOUR_KEY_HERE>. More examples are shown in Step 2 below.

Left: Enphase Gateway Local Web View; Right: Testing API Calls in a Browser

Before we start in with the tasks, let's list the software components and hardware components we are using in the tutorial.

Software Components

A Web service built with C# and a simple web page to display the results from that web service. Both are running in a free Windows Azure web instance.

Why a web service? We can hide our Enphase API key and the web service is easy to create and use. You can have code for retrying or aggregation of different streams of data. Also, the web service can be leveraged from other clients (applications on other devices).
Why Windows Azure? Because we have a number of other projects hosted there and it made sense. They offer a free web site solution that is easy to use.
Is a hosting solution like Windows Azure necessary? No you can host the web service and web page on your local computer and it would work fine. We wanted to host the service in the Cloud so we could access it remotely.
What operating systems did we use for this tutorial? Development was done on both Windows 7 and Windows 8.

jQuery - a JavaScript library to simplify HTML Ajax interactions.

Why? It’s easy to use jQuery in a web page to call the web service we created and put the data on a web page.

WebMatrix or Visual Studio - development tools that can publish to a Microsoft Azure web instance.

Why? Free and relatively easy to use tools for creating web sites. The web sites can be used locally only and also published to a remote web site.

Enphase API

Why? Well, because this API provides the access to the data about our system. Thankfully, it is a fairly simple API to use with query strings that require your “key”. With each “call” to the API you can get different types of data back.

Sample code files for this blog post can be downloaded from Github.

Hardware Components

Enphase Envoy Comunications Gateway

The Enphase Envoy Comunications Gateway connects to a router (https://enphase.com/en-us/products-and-services/envoy) which talks to the Enphase web service. The Envoy in turn communicates with the micro-inverters that convert DC to AC, one for each solar panel.
Our solar array consists of 14 panels on our roof. Each panel is a 255 W, SolarWorld, mono-crystalline, 60 cell solar panel. Here is a summary: https://enlighten.enphaseenergy.com/public/systems/zVU7148952
The solar panels were designed and installed by Solterra Systems.

Specify summary_date for a specific day.
https://api.enphaseenergy.com/api/systems/XXXXXX/summary?summary_date=2013-01-02&key=11112222333344441111222233334444

Step 3: Setting up a Free Azure Web Site

All the code shown in this step and the next (Step 4) will run locally and don’t require a remote web site. If you you only want to experiment with a local web site (on your computer), just skip the tasks that talk about creating a Azure web site and publishing remotely.

Step 3.1: Go to https://manage.windowsazure.com, create the site and download the publishing settings for the site.

Assuming you already have an account established, you will create a free Azure web instance. In the Windows Azure Free instance, your web site runs in a multi-tenant environment, that is, you share resources. This is fine for what we are doing here.
We call the site in this tutorial “solarmarx” which gets the domain name http://solarmarx.azurewebsites.net. Call your site something appropriate for your situation. If you wanted to have a custom domain (like www.mycustomdomain.com), you can do that as an extra step.
After you create the site, download the publishing settings which are used to tell you local programs (WebMatrix and Visual Studio Express) how to publish to the remote web site (in the Cloud).

Step 3.2: Create a local web site.

Create a site using WebMatrix or Visual Studio. Create an empty site then associate the site with the publishing settings. You can also create an fully functional local site first and and test it locally and then later associate the publishing profile.

Step 3.3: Make a change to your web site locally and publish to the remote site and verify.

For example, edit the title of the Default.cshtml document and put some text in the body of the HTML file.

<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="utf-8" />
        <title>Solarmarx</title>
        <link href="~/favicon.ico" rel="shortcut icon" type="image/x-icon" />
    </head>
    <body>
        <p>Welcome to Solarmarx!</p>
    </body>
</html>

Select the Default.cshtml, right-click, and select Publish.

Step 3.4: In the Azure Management Portal for the web site, make sure Default.cshtml is one of the default document types for the web site.

Go to the Configure page of the web site and look for the default documents section.
Add Default.cshtml as a document type.

Left: Windows Azure Web Sites View, Right: Windows Azure – Creating a Web Site

Left: Windows Azure Download Publishing Profile; Right: Setting Default Documents

Step 4: Create a Simple Web Service and Display Information

In this step of the tutorial, we show using Visual Studio Express 2012. You could also do the same work in WebMatrix2. You have several options for working with the web site you created. To open the site in Visual Studio Express 2012, use "Open Web Site" and find the Local IIS web site "Solarmarx" in our case.

Step 4.1: Create a web service by create a new .asmx file.

Left: Create a new Web Service; Right: What Gets Created

Step 4.2: Put the code into the WebService.cs file as shown below. Below, an example key (11112222333344441111222233334444) is used. As well XXXXXX is used as the system ID. Fill in the correct values for your system.

using System;
using System.IO;
using System.Net;
using System.Text;
using System.Web.Services;

[WebService(Namespace = "http://solarmarx.com/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
// To allow this Web Service to be called from script, using ASP.NET AJAX, uncomment the following line. 
[System.Web.Script.Services.ScriptService]
public class WebService : System.Web.Services.WebService {

    public WebService () {

        //Uncomment the following line if using designed components 
        //InitializeComponent(); 
    }

    [WebMethod]
    public string HelloWorld() {
        return "Hello World";
    }

    [WebMethod]
    public string GetEnphaseStats()
    {
        String key = "11112222333344441111222233334444";
        String uri = "https://api.enphaseenergy.com/api/systems/XXXXXX/summary?key=" + key;
        WebRequest wrGETURL = WebRequest.Create(uri);

        Stream objStream = wrGETURL.GetResponse().GetResponseStream();

        StreamReader objReader = new StreamReader(objStream);

        StringBuilder sb = new StringBuilder();
        String sLine = "";

        while (sLine != null)
        {
            sLine = objReader.ReadLine();
            if (sLine != null)
                sb.Append(sLine);
        }
        return sb.ToString();
    }
    
}

Step 4.3: Test the web service locally (on your computer) by selecting the WebService.asmx and browsing.

Left: Browsing a Web Service Locally; Right: The Service Operations

Step 4.4: Create a basic web page that uses jQuery.

<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="utf-8" />
        <title>Solarmarx</title>
        <link href="~/favicon.ico" rel="shortcut icon" type="image/x-icon" />
        <script src="~/Scripts/jquery-1.8.3.min.js"></script>
        <script>
            $(document).ready(function () {
                alert('jQuery installed.');
            });
        </script>
    </head>
    <body>
        <p>Welcome to Solarmarx!</p>
    </body>
</html>

Install jQuery in a \Scripts folder. You can use the NuGet service to do that.
Test that you have installed jQuery correctly by making the changes shown above and viewing the Default.cshtml page

Step 4.5: Modify the web page as shown below to add script that calls the web service and puts the results in an HTML element on the page.

<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="utf-8" />
        <title>Solarmarx</title>
        <link href="~/favicon.ico" rel="shortcut icon" type="image/x-icon" />
        <script src="~/Scripts/jquery-1.8.3.min.js"></script>
        <script>
            var webservicePath = "/WebService.asmx/";
            var pubLink = "https://enlighten.enphaseenergy.com/public/systems/zVU7148952";

            $(document).ready(function () {
                $.ajax({
                    type: "POST",
                    url: webservicePath + "GetEnphaseStats",
                    success: function (results) {
                        var res = jQuery.parseJSON($(results).text());
                        var avg_use = 24; // kWh per day
                        var d = new Date().toLocaleString();
                        var current_power = res.current_power;
                        var energy_today = res.energy_today / 1000;
                        var energy_lifetime = res.energy_lifetime / 1000;
                        var energy_today_perc = 100 * (energy_today / 24);
                        var summaryElement = $("<span id=\"enphaseTitle\">Solar Summary</span> <br/>" +
                                                "<span> Current power: <a target=\"_blank\" href=\"" + pubLink + "\">" + current_power + "W</a> at " + d + "</span > <br/>" +
                                                "<span> Energy generated today: " + energy_today + " kWh (" + energy_today_perc.toFixed(1) + "%*)</span> <br/>" +
                                                "<span> Energy generated lifetime: " + energy_lifetime + " kWh</span> <br/>" +
                                                "<br/><span id=\"note\">* typical daily usage of 24 kWh</span>");
                        $("#enphaseStats").append(summaryElement);
                    },
                    error: function (result) {
                        alert(result.responseText);
                    }
                });
            });
    </script>
    </head>
    <body>
        <p>Welcome to Solarmarx!</p>
        <!-- data from webs service call goes here -->
        <div id="enphaseStats">    
        </div>
    </body>
</html>

Step 5.5: If publishing remotely, you need to set configure HttpPost as a service that can be used. This is done in the web.config file.

Step 5.6: Test locally, publish to the cloud (if you created a remote site), and test remotely.

TravelMarx

Pages

Sunday, January 19, 2014

Solar in Seattle – One Year of Data

Sunday, January 20, 2013

Note On Using the Enphase Power Today Method

Problem

Solution

Details

Sunday, January 13, 2013

Working with Your Solar Array Data Using the Enphase API

Overview

Software Components

Hardware Components

Step 1: Get an Enphase API Key

Step 2: Get Familiar with Enphase Data Using the API

API: Get System Info

Example Input

Example Output

API: Get Lifetime Energy

Example Input

Example Output

API: Get Power Today

Example Input

Example Output

Get Summary

Example Input

Example Output

Notes

Step 3: Setting up a Free Azure Web Site

Step 4: Create a Simple Web Service and Display Information